DESC:FIELD OF THE DISCLOSURE
The present disclosure generally relates to the field of structural members, and more particularly, to a lightweight structural member with enhanced strength.
BACKGROUND
This section is intended to provide information relating to the technical field and thus, any approach or functionality described below should not be assumed to be qualified as prior art merely by its inclusion in this section.
The trends in various industries, such as aerospace, automotive, and construction, are leaning towards the use of lightweight structural designs. Conventional structural designs often prioritize strength and rigidity at the expense of weight. The existing lightweight structural designs often fail to support weight, resulting in sudden and unforewarned buckling. Furthermore, lightweight structural designs also generate resonance when subjected to high-frequency harmonic loads, leading to vibration-induced fatigue failures and unintended kinematics.
For example, structural or compressive members are prevalent in mechanical components and structures. When these components are subjected to high-frequency harmonic loads, resonance occurs which may cause vibration-induced fatigue failures and unintended kinematics. Further, severe compressive loads can result in buckling, which occurs suddenly and without warning. Likewise bending is an issue in both static and dynamic structures.
Thus, the need for lightweight structural designs with superior mechanical properties has become increasingly important in various applications. In applications like racing bicycles, frames must be both robust and lightweight. Similarly, in rotating shafts, conflicting demands arise between the need to add material for torque transmission and remove material to increase speeds. In the case of an engine pushrod, which has a hollow interior, simply reducing the mass of the pushrod using any conventionally available technique could potentially compromise its stiffness, resulting in undesired characteristics such as sloppiness, noise, vibrations, buckling, and the like. Therefore, it is crucial to maintain the lightness of the structural member while ensuring that its strength or stiffness is not compromised.
In applications such as pushrod, which is often subject to wear and tear, heavy pushrods can induce metal chipping, spalling, and further wear. The wear debris produced often mixes with the lubricating oil accelerating the wear. It also contaminates the engine oil, necessitating more frequent oil changes.
Conventional pushrods may also face environmental issues, such as low-frequency resonance. Heavier components resonate at lower frequencies, affecting valve train dynamics and directly impacting engine life. This low-frequency resonance can cause vibration-induced fatigue. Additionally, pushrods can incur breakdown costs. For example, engine failures result in significant downtime, leading to productivity loss and repair expenses.
Therefore, in view of the existing limitations, there exists a need for developing a lightweight structural member with improved mechanical properties to address the limitations of conventional designs like wear and tear, low frequency resonance, sloppiness, noise, vibrations, buckling and vibration-induced fatigue.
SUMMARY
This section is provided to introduce certain objects and aspects of the present disclosure in a simplified form that are further described below in the detailed description. This summary is not intended to identify the key features or the scope of the claimed subject matter.
It is an object of the present disclosure to provide a lightweight structural member with enhanced mechanical properties such as stiffness, strength and reliability.
It is another object of the present disclosure to provide a lightweight structural member with enhanced strength-to-weight ratio that withstands high stresses without adding significant weight.
It is another object of the present disclosure to provide a lightweight structural member that effectively mitigates noise, vibration, and harshness, ensuring a more comfortable and refined user experience.
It is another object of the present disclosure to provide a lightweight structural member that possesses higher natural frequencies, enhancing its stability and resistance to resonance.
It is another object of the present disclosure to provide a lightweight structural member that possesses higher natural frequencies thereby enhancing its stability and resistance to resonance.
Conventional designs aim to ensure structures can withstand heavy loads, high stress, or extreme conditions without breaking or deforming. Achieving high strength and rigidity typically involves using dense and heavy materials like solid steel, concrete, or cast iron. While these materials provide the desired mechanical properties, the added weight introduces several disadvantages such as increased energy consumption, reduced efficiency and performance, higher transportation and material costs, and limitations in design flexibility for weight-sensitive applications. For example, Conventional structures made of solid steel are very strong but extremely heavy, making them unsuitable for aircraft design, where minimizing weight is crucial for fuel efficiency and performance.
Further, in conventional systems, unwanted noise and vibrations originate from mechanical operations, environmental factors, or resonance within a structure that reduce durability and user comfort. Every structure has a natural frequency at which it tends to vibrate when subjected to an external force. When the frequency of an external force matches the natural frequency of a structure, it amplifies vibrations, leading to instability, damage, or failure.
The present disclosure overcomes the above disadvantages by providing a lightweight structural member with enhanced mechanical properties such as stiffness, strength and reliability.
The present disclosure provides a lightweight structural member with sound-absorbing and vibration or impact-damping materials that prevent the transmission of noise or harsh vibrations, ensuring a more comfortable user experience.
The present disclosure discloses a lightweight structure member that provides higher performance by enhancing the strength of the lightweight structure under internal pressure by a phenomenon known as stress-stiffening. In an example, lightweight structure members like pneumatic tires and balloons, exhibit improved structural integrity when pressurized.
The present disclosure provides a lightweight structural member that possesses higher natural frequencies. Structures with higher natural frequencies are less likely to experience resonance from common sources of vibration (e.g., machinery, vehicles, or environmental forces) because most external forces have lower frequencies. This improves stability, increases resistance to resonance thereby extending the structure's lifespan.
The present disclosure provides a lightweight structural member that exhibits superior kinematic fidelity, enabling precise and accurate movement transmission. This ensures that the structural maintains its intended motion characteristics (e.g., flexibility, rigidity, or damping) under varying loads and vibrations. For example, a car's chassis designed with high kinematic fidelity will accurately dampen road-induced vibrations and noise and maintains precise alignment of moving parts like suspension systems.
The present disclosure provides a lightweight structural member that effectively resists buckling, when a compressive load causes a member to deform laterally or collapse thereby ensuring structural integrity under compressive loads.
In one aspect of the present disclosure, a structural member may be provided. The structural member may include an outer surface, an inner surface, an elongated cavity extending along a longitudinal axis of the structural member, a functionally graded foam arranged within the elongated cavity along the longitudinal axis. The functionally graded foam may include an inner foam surface and an outer foam surface, and a layer arranged between the inner surface and the outer foam surface.
In some embodiments of the present disclosure, the functionally graded foam may be one of a metallic foam and a non-metallic foam.
In preferred aspects of the present disclosure, the functionally graded foam having varying densities may be arranged within the elongated cavity.
In preferred aspects of the present disclosure, the density of the functionally graded foam may be minimum at a first end and a second end of the structural member, and wherein the density of the functionally graded foam may be maximum at a centre of the structural member.
According to an embodiment of the present disclosure, the functionally graded foam having varying densities may be continuously casted or formed within the elongated cavity along the longitudinal axis.
According to an embodiment of the present disclosure, the functionally graded foam may be selected from an open cell foam.
According to an embodiment of the present disclosure, the functionally graded foam having varying wall thickness may be arranged within the elongated cavity, and wherein the functionally graded foam is at least an open cell foam or a closed cell foam.
According to an embodiment of the present disclosure, the elongated cavity may be filled with an inert gas under a specified pressure to interact with the functionally graded foam.
According to an embodiment of the present disclosure, the elongated cavity may be filled with at least one volatile substance to interact with the functionally graded foam.
According to an embodiment of the present disclosure, the layer may include at least one of an adhesive material layer or a metal layer that facilitates attachment of the functionally graded foam with the inner surface of the structural member.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated herein, and constitute a part of this disclosure, illustrate exemplary embodiments of the disclosed methods and systems in which like reference numerals refer to the same parts throughout the different drawings. Components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present disclosure.
Although exemplary connections between sub-components have been shown in the accompanying drawings, it will be appreciated by those skilled in the art, that other connections may also be possible, without departing from the scope of the disclosure. All sub-components within a component may be connected to each other, unless otherwise indicated.
Stress stiffening refers to the phenomenon where a flexible structure becomes stiffer under the influence of external loads. This is often observed in slender structures or members subjected to axial loads, such as cables, membranes, and certain types of beams. Stress stiffening is a result of material's response to the applied load.
In simple terms, when a flexible structure is subjected to an axial load or tension, the material experiences both axial deformation and transverse deformation. Stress stiffening occurs because the transverse deformation of the material contributes to an increase in stiffness, making the structure appear stiffer than it would be under the same axial load in the absence of transverse deformation.
A classic example is a cable or a slender rod under tension. As the tension force is applied, the material experiences not only elongation but also a decrease in its cross-sectional area due to Poisson's effect. This reduction in cross-sectional area results in an increase in axial stiffness, leading to stress stiffening. Another example is a balloon under internal pressure.
Figure 1a and 1b illustrate schematic diagrams of a conventional engine pushrod of an internal combustion engine.
Figure 2 illustrates a cross-sectional view of a conventional pushrod.
Figures 3 and 4 illustrate schematic diagrams of a pushrod depicting buckling in different vibration modes.
Figure 5 illustrates a cross-sectional diagram of a pushrod with reinforcement according to the present disclosure.
Figure 6 illustrates a hollow structural member according to an embodiment of the present disclosure.
Figure 7 illustrates a cross-sectional diagram of a pushrod according to an embodiment of the present disclosure.
Figure 8 illustrates a cross-sectional diagram of a drive shaft according to an embodiment of the present disclosure.
Figure 9 illustrates a cross-sectional diagram of a pushrod according to another embodiment of the present disclosure.
Figure 10 illustrates a cross-sectional diagram of a drive shaft according to another embodiment of the present disclosure.
The foregoing shall be more apparent from the following more detailed description of the disclosure.
DESCRIPTION OF THE DISCLOSURE
Exemplary embodiments now will be described with reference to the accompanying drawings. The disclosure may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey its scope to those skilled in the art. The terminology used in the detailed description of the particular exemplary embodiments illustrated in the accompanying drawings is not intended to be limiting. In the drawings, like numbers refer to like elements.
The specification may refer to “an”, “one” or “some” embodiment(s) in several locations. This does not necessarily imply that each such reference is to the same embodiment(s), or that the feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments.
As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless expressly stated otherwise. It will be further understood that the terms “include”, “comprises”, “including” and/or “comprising” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It will be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. Furthermore, “connected” or “coupled” as used herein may include wirelessly connected or coupled. As used herein, the term “and/or” includes any and all combinations and arrangements of one or more of the associated listed items.
The term “pushrod” refers to a rod operated by cams that opens and closes the valves in an internal combustion engine.
The term “engine” refers to any device for converting some forms of energy into mechanical work.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of the ordinary skills in the art to which this disclosure pertains. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
In the following description, for the purposes of explanation, numerous specific details have been set forth in order to provide a description of the disclosure. It will be apparent, however, that the disclosure may be practiced without these specific details and features.
Conventionally, pushrods of an engine are used to reduce the inertial forces within the engine, enhance fuel efficiency, increase engine responsiveness, reduce wear and tear, increase rotations per minute (RPM), and provide better balance and vibration control.
Figure 1a and 1b illustrates a schematic diagram of a conventional engine pushrod in an internal combustion engine. As the camshaft 2 rotates, the pushrod 1 transmits motion to the rocker arm 3, which in turn operates the engine valves 4. In a four-stroke cycle, the camshaft 2 rotates at twice the engine speed. Assuming a maximum engine speed of 4000 rpm, the pushrod's motion frequency is 133 Hz. For a pushrod with a length of 15 cm, an outer diameter of 10 mm, a wall thickness of 3 mm, and a cam throw of 5 mm, the pushrod's inertia force can be calculated as follows:
Density of steel, ??=8000 kg/m3
Mass of the pushrod, ??=8000×?? (102-42)/4×15×10-8=0.05 kg = 80 gm
Time taken for the pushrod to reach 5 mm distance (quarter camshaft rotation), ??=1/133×4=0.002 ??????
Maximum velocity of the pushrod is achieved at 0.001 sec when the push-rod is at midway, i.e., 2.5 mm travel
Acceleration of the pushrod midway, ??=2.5×10-3/0.0012=2500??/??????2˜250 ??
Inertia force due to this mass, ??=????=0.08×2500=200 ??
In other words, at an engine speed of 4000 rpm, a conventional pushrod that weighs a mere 80 gram would develop a maximum dynamic force of 20 kgf on the camshaft and rocker arm. This causes pounding of the camshaft and rocker arm with a hammer. Additional drawbacks arise at higher engine speeds, particularly when the valve spring weakens and loses stiffness. The loss of dynamic stiffness leads to valve train surge, a potentially catastrophic event. The pushrod serves as a force transmitter, not as a component that burdens both the tappet and rocker arm with its own inertia forces. Excessive inertia forces could cause the pushrod to jump due to out-of-phase movements that may not align with the cam's contours. These forces can also lead to accelerated wear and tear, compromising engine reliability.
Figure 2 illustrates a cross-sectional view of a conventional pushrod. Conventionally, the pushrod has a hollow interior that causes vibration-induced fatigue that results in buckling under severe compressive stress suddenly thereby reducing its performance.
The pushrod may be subject to loss of engine efficiency due to a worn-out camshaft or tappet can reduce engine efficiency, leading to increased fuel consumption.
The pushrod often generates noise, especially when high inertia loads can generate excessive noise. To reduce the noise, enhance the stability, resistance to resonance and improve durability and performance, the natural frequency of the lightweight structure has to be enhanced. The first natural frequency of a system is given by the following equation:
??=v??/??
To increase the natural frequency, either the structural stiffness has to be augmented or the mass has to be diminished. However, reducing the mass of the pushrod could potentially compromise its stiffness, resulting in undesired characteristics such as sloppiness, noise, vibrations, and even buckling.
While achieving high structural strength requires increasing mass, maintaining a high natural frequency necessitates reducing mass.
Therefore, there is a need for a lightweight structure with enhanced stiffness to overcome the above-mentioned problems of conventional pushrods. The structure's mass must be minimized without compromising strength.
Buckling is the sudden change in shape (deformation) of a structural component under load, such as the bowing of a column under compression or the wrinkling of a plate under shear. If a structure is subjected to a gradually increasing load, when the load reaches a critical level, a member may suddenly change shape, and the structure and component is said to have buckled.
Buckling may occur even though the stresses that develop in the structure are well below those needed to cause failure in the material of which the structure is composed. Further loading may cause significant and somewhat unpredictable deformations, possibly leading to complete loss of the member's load-carrying capacity.
Figures 3 and 4 illustrate schematic diagrams of conventional pushrod depicting buckling in different vibration modes. The conventional pushrod is subject to various failures modes such as buckling due to lateral instability inherent in slender structures under axial compressive loading. If the load on a column is applied through the center of gravity (centroid) of its cross section, it is called an axial load. The structure may suddenly become unstable, leading to a severe loss of load-bearing capacity and engine failure. This is represented by point B in Figure 3. In Figure 3, the push rod experiences buckling at antinode B, where there is maximum strain energy dissipation.
Another example of buckling is pushrod according to another vibration mode is illustrated in Figure 4. In Figure 4, the push rod experiences buckling at antinodes D and E, where there is maximum strain energy dissipation.
In order to address the above-mentioned problems, the present disclosure proposes a solution to significantly decrease the weight of the pushrod (or any hollow column under compressive stress) without sacrificing functionality. The disclosure proposes a solution to concurrently boost stiffness and reduce mass. The present disclosure proposes a lightweight structural member that provides enhanced mechanical properties such as stiffness and strength and enhanced system reliability.
The present disclosure provides an innovative approach to enhance pushrod design, enabling improved performance even at higher engine speeds. The present disclosure provides a pushrod with reinforcement. Selective reinforcement of the pushrod requires consideration of at least the first two modes, depicted in Figure 3 and Figure 4. The antinode for the first mode is at location B, and for the second mode, it would be locations D and E. These two modes exhibit the highest strain energy dissipation.
For example, Figure 5 illustrates a cross-sectional diagram of a structural member or pushrod 100 with reinforcement.
Selective pushrod 100 reinforcement involves stepped machining of the pushrod wall, a process that is not only cumbersome but also introduces stress raisers due to sharp corners and geometric discontinuities, as illustrated in Figure 5. It also increases the component weight. The wall thickness of the reinforcement is carefully determined to prevent buckling from the applied forces and resonance from the harmonics.
Figure 6 illustrates a hollow structural member according to the present disclosure.
The present disclosure provides a structural member 100. As used herein, the structural member refers to a component or element that contributes to the overall stability, strength, and load-bearing capacity of the structure. In an embodiment of the present disclosure, the structural member is a solid structural member that has a continuous, solid cross-section without any internal void. In another embodiment of the present disclosure, the structural member is a hollow structural member that has a hollow or empty cross-sectional shape and is used in engineering and construction for various applications. The hollow structural member is required where the weight of the structural element may be reduced while often maintaining a significant portion of its strength. The hollow structural members often have rectangular or circular shape.
As illustrated in Fig. 6, the structural member 100 is a hollow body made of a material with a high strength-to-weight ratio. The wall thickness of the structural member 100 is designed to prevent buckling under applied compressive forces and to mitigate resonance caused by harmonic vibrations. This optimization balances the need for reducing the member’s mass without compromising its structural strength. Maintaining a high natural frequency typically requires reducing the mass whereas achieving high structural strength requires increasing mass. The present disclosure addresses the inherent trade-off between the two conflicting requirements of maintaining a high natural frequency and achieving high structural strength. The present disclosure employs advanced materials and optimized geometry to achieve both the objectives of ensuring stability and performance under dynamic conditions.
The structural member 100 that includes an outer surface 102 and an inner surface 104. Furthermore, there may be one or more components of the structural member 100, and the same is not shown in the Fig. 6 for clarity.
The structural member 100 includes an outer surface 102. The outer surface refers to outer region of the structural member. The structural member includes an inner surface 104. The inner surface refers to the inner region of the structural member.
The structural member 100 includes an elongated cavity 106 extending along a longitudinal axis of the structural member. As used herein, an elongated cavity refers to a hollow space within the structural member.
The structural member 100 includes a functionally graded foam 108 arranged within the elongated cavity along the longitudinal axis. As used herein, the longitudinal axis refers to an imaginary line running lengthwise in a longitudinal direction through the centre of the structural member. The functionally graded foam includes an inner foam surface 118 and an outer foam surface 112. The inner foam surface 118 corresponds to an inner region of the functionally graded foam while the outer foam surface 112 corresponds to the outer region of the functionally graded foam as also shown in Fig. 6.
The structural member 100 also includes a layer 114 arranged between the inner surface 104 of the structural member and the outer surface 112 of the functionally graded foam. The layer 114 includes at least one of an adhesive material layer or a metal layer that facilitates attachment of the functionally graded foam with the inner surface of the structural member.
As used herein, foam refers to a material that is typically composed of a network of gas-filled bubbles or pores or cells trapped within a solid or liquid matrix. The properties of foam, such as density, porosity, and elasticity, may vary widely depending on the specific composition and manufacturing process of the foam. In general, foam is known for its lightweight nature, and flexibility.
More particularly, functionally graded foam, as used herein, refers to a type of foam material whose properties vary systematically or continuously across its volume. The functionally graded foams are designed to exhibit specific variations in properties such as density, porosity, and stiffness along a specific direction or within specific regions. The purpose of functionally graded foam is to optimize the weight distribution of any structural material.
In an embodiment of the present disclosure, the functionally graded foam 108 may either be inserted into the structural member 100, or it may be formed inside the structural member 100.
In an embodiment of the present disclosure, the functionally graded foam 108 may be a metallic foam used for high strength and stiffness while in another embodiment of the present disclosure, the functionally graded foam may be a non-metallic foam.
In an embodiment of the present disclosure, the metallic foam is composed of metal such as aluminium, nickel or titanium. In another embodiment, the metallic foam is composed of metal alloys. As used herein, the non-metallic foam may include materials which are not metals such as polymers, ceramics or any composite material.
In another embodiment of the present disclosure, the functionally graded foam 108 may be an open cell foam or a closed cell foam or a combination thereof. As used herein, the closed cell foam refers to a type of foam structure characterized by sealed, non-interconnected cells within the material. Closed cell foam contain tiny spaces, or cells, or pores that are entirely closed and contained. Each pore or bubble or cell is completely enclosed, so the cells do not share walls, making the foam rigid, strong, and possess high elastic stiffness and high strength-to-weight ratio. As uses herein, an open cell foam is a type of foam in which the cells or bubbles are not completely enclosed but are interconnected, creating a porous structure.
In another embodiment of the present disclosure, the functionally graded foam 108 may be a regular shaped foam having constant wall thickness arranged or formed inside the structural member along the longitudinal axis. The functionally graded foam 108 of constant wall thickness may have varying density. For example, the functionally graded foam 108 with constant wall thickness may have lowest or minimum foam density at the ends and highest foam density at the centre, wherein the density of the foam progressively increases towards the centre.
In another embodiment of the present disclosure, the functionally graded foam 108 may be an irregular shaped foam arranged or formed inside the structural member along the longitudinal axis. The functionally graded foam with such irregular shape may have uniform density or non-uniform density. In an example, the functionally graded foam 108 may have irregular thickness, wherein the lowest or minimum thickness is at the ends and highest or maximum thickness is at the centre, and wherein the thickness of said foam progressively increases towards the centre. In another example, the functionally graded foam may be in the form a step when moving from the edges towards the centre of the structural member.
In another embodiment of the present disclosure, the structural member 100 may be filled with an inert gas such as nitrogen under a specified pressure which interacts with the functional graded foam to enhance the structural strength by way of stress stiffening.
In another embodiment, the structural member 100 may be filled with at least one volatile substance e.g., camphor or similar material. When the structural member is driven at high speed, the temperature and duty cycle of structural member would increase and therefore the volatile substance would form vapours. Further, vapours would exert vapour pressure i.e., increasing internal pressure while interacting with the foam, thereby further enhancing structural strength.
In another embodiment of the present disclosure, the structural member 100 may be filled with an inert gas or a volatile substance or a combination of both the inert gas and the volatile substance.
In another embodiment of the present disclosure, the structural member 100 may be a pushrod and a draft shaft.
Figure 7 illustrates a cross-sectional diagram of a pushrod according to an embodiment of the present disclosure.
The pushrod as depicted in Fig. 7 may be substantially similar to the structural member depicted in Fig. 6 and thus, the features common to both the pushrod and structural member have not been repeated for the sake of brevity.
According to the embodiment of Fig. 7, the functionally graded foam may be an open cell foam extending across the elongated cavity of the structural member or pushrod 100.
In an embodiment of the present disclosure, the functionally graded foam 108 may either be inserted into the pushrod, or it may be formed inside the pushrod. The functionally graded foam 108 is a regular shaped foam having constant wall thickness arranged or formed inside the pushrod along the longitudinal axis.
In an embodiment, the functionally graded foam of constant wall thickness may have varying density. In an example, as illustrated in Fig. 7, the density of the functionally graded foam is minimum or lowest at the ends first end 116 and second end 118 of the structural member 100. For example, density of the functionally graded foam 108 is minimum at a lower end and an upper end of the pushrod while the density of functionally graded foam is maximum at the centre. In another example, the density of the functionally graded foam progressively increases from the ends of the pushrods towards the centre.
In another embodiment, the structural member or pushrod 100 is filled with an inert gas such as nitrogen under a specified pressure which interacts with the functional graded foam to enhance the structural strength by way of stress stiffening.
In another embodiment, the structural member 100 may be filled with at least one volatile substance e.g., camphor or similar material. When the pushrod is driven at high speed, the temperature and duty cycle of pushrod would increase and therefore the volatile substance would form vapours. Vapours would exert vapor pressure i.e., increasing internal pressure while interacting with the foam, thereby further enhancing structural strength.
In another embodiment, the structural member 100 may be filled with an inert gas or a volatile substance or a combination of both the inert gas and the volatile substance.
As illustrated in Figure 7, the pushrod with open cell foam is described. In the present disclosure, by combining a reduced wall thickness, functionally graded foam, internal gas under pressure, and a readily vaporizable solid and / or liquid, a remarkable level of compressive strength is achieved. There is a thin layer of adhesive between the outer surface of the foam and the inner surface of the tube. Alternately, metal bonding could also be created if applicable. The foam density may be adjusted to match the specific functional demands of the component, ensuring optimal performance throughout its operational range. This feature ensures that there are no abrupt geometric discontinuities and stress raisers. In the illustrative case of a pushrod, the foam density could be low at either end and progressively increase to the maximum towards the centre, ensuring a smooth transition and eliminating abrupt geometric discontinuities.
Further, thin-walled structures exhibit a phenomenon known as stress-stiffening, where they can withstand significant compressive loads when pressurized. Further, the inert gases like nitrogen, which don't adversely react with metals, contribute to bearing compressive loads alongside the foam. Incorporating a few granules of a sublimating solid like camphor or a small amount of volatile liquid further elevates the pressure as the pushrod's temperature and duty cycle increases. Additionally, the functionally graded open-cell foam within the pushrod effectively fills the hollow space and resists lateral instability (buckling), thereby enhancing the component’s ability to withstand compressive loads. Since gas pressure is utilized to enhance structural stiffness, open-cell foam is necessary to ensure the unobstructed movement of gases within the component. The foams can be continuously cast or formed into pellets of varying densities and stacked appropriately. The specific design parameters can be calculated and applied contextually. This design strategy results in an "anti-fragile" component, meaning it grows stronger with increasing temperature, up to a certain point. The disclosure also offers the advantage of minimal engine oil contamination due to wear debris, resulting in extended engine life and smoother operation. Moreover, the design eliminates abrupt geometry changes and can be seamlessly integrated within the prevailing component design space without requiring additional space outside the component boundary.

Figure 8 illustrates a cross-sectional diagram of a high-torque a drive shaft according to an embodiment of the present disclosure.
The drive shaft as depicted in Fig. 8 may be substantially similar to the structural member 100 depicted in Fig. 6 and thus, the features common to both the drive shaft and structural member have not been repeated for the sake of brevity.
According to the embodiment of Fig. 8, the functionally graded foam may be an open cell foam extending across the elongated cavity 106 of the drive shaft.
As can been seen in Fig. 8, the high-torque drive shaft 300 that is configured with an open cell foam includes universal joints 302a, 302b at a first and second ends, reinforcing sleeves 304a, 304b at first and second ends, hermetic seals 310a, 310b at first and second end, and an outer sleeve 312.
According to an embodiment of the present disclosure, the functionally graded foam or open cell foam 308 has low density adjoining hermetic seal 306a, 306b at first and second end of the high-torque drive shaft. Moreover, the density of the open cell foam 308 progressively increases from the first end to centre region and progressively decreases from the centre region toward the second end.
In an embodiment of the present disclosure, the functionally graded foam is a regular shaped foam having constant wall thickness arranged or formed inside the drive shaft along the longitudinal axis. Further, the functionally graded foam 308 of constant wall thickness may have varying density. The density of the functionally graded foam 308 is minimum at a first end 306a and a second end 306b of the drive shaft. The density of the functionally graded foam 308 is maximum at a centre 309 of the drive shaft.
In an embodiment of the present disclosure, the density of the functionally graded foam 308 progressively increases from the first end and the second end of the drive shaft towards the centre of the drive shaft to add more strength to the centre of the drive shaft and to prevent buckling. The functionally graded foam varying densities is continuously casted or formed within the elongated cavity along the longitudinal axis.
In an embodiment of the present disclosure, the elongated cavity 106 is filled with an inert gas such as nitrogen under a specified pressure to interact with the functionally graded foam. The inert gas interacts with the functionally graded foam to enhance structural strength by way of stress stiffening. Further, the inert gas is inserted into the elongated cavity of the drive shaft on a permanent basis.
In another embodiment of the present disclosure, the elongated cavity 106 is filled with volatile substances such as camphor to further enhance the structural strength of the member. In accordance with the implementation of the present disclosure, when the drive shaft is driven at high speed, the temperature and duty cycle of drive shaft increases and therefore the volatile substance would form vapours. The formed vapours exert vapor pressure i.e., increase internal pressure while interacting with the open Cell foam, thereby further enhancing structural strength.
In another embodiment of the present disclosure, the elongated cavity 106 may be filed with insert gas or volatile substance, or combination of the inert gas and the volatile substance under a specified the volatile substance to enhance the structural strength of the member such as solid steel pipe.
As used herein, the open cell foam refers to a type of foam wherein open pores or cells are interconnected within the material. In open-cell foam, the cell walls have openings or windows, allowing air, liquids, and gases to move freely through the material.
According to Fig. 8, the drive shaft 300 with open cell foam is depicted. In such an embodiment, the draft shaft 300 transmits torque between a power source and the point at where it is utilized. In an automobile, the drive shaft connects the drive axle to the gearbox. There are other applications such as in helicopters, machineries, etc., where high speeds are encountered. The design of the propeller shaft involves conflicting demands: the torque transmission requires more material while the need to keep the unbalanced forces to the minimum and maximize the natural frequency requires reduction in component mass.

An important factor deciding on drive shaft design is a factor called “critical speed”. The critical speed of a rotating shaft is the speed at which the shaft begins to resonate or vibrate excessively. Resonance is typically caused by the natural frequency of the shaft matching the frequency of the forces acting on it during rotation. When a shaft operates at or near its critical speed, the amplitude of vibrations can increase significantly, leading to potential mechanical failure or damage. This is particularly critical in applications where precise and smooth operation is essential, such as in machinery or high-speed rotating equipment.
The disclosure provides and offers a way to reduce the weight of the drive shaft while providing a means to increase its critical speed. The disclosure offers a solution to reduce the tube wall thickness of the driveshaft by inserting functionally graded open cell foams. The material of the tube and foam could depend on the type of application.
Figure 9 illustrates a cross-sectional diagram of a pushrod according to another embodiment of the present disclosure.
The pushrod as depicted in Fig. 9 may be substantially similar to the structural member depicted in Fig. 6 and thus, the features common to both the pushrod and structural member have not been repeated for the sake of brevity.
According to the embodiment of Fig. 9, the functionally graded foam 108 may be an open cell foam or a closed cell foam extending across the elongated cavity 106 of the structural member or pushrod 100.
In an embodiment of the present disclosure, the functionally graded foam 108 may either be inserted into the pushrod, or it may be formed inside the pushrod. The functionally graded foam 108 is an irregular-shaped foam having irregular thickness arranged or formed inside the pushrod along the longitudinal axis.
In an embodiment of the present disclosure, the functionally graded foam of varying or irregular thickness may have a uniform density or a non-uniform density. In an example, as illustrated in Fig. 9, the thickness of the functionally graded foam 108 is minimum or lowest at the ends e.g., a lower/first end and an upper/second end of the pushrod while the thickness of the functionally graded foam is maximum at the centre. In another example, the thickness of the functionally graded foam progressively increases from the ends of the pushrods towards the centre. In another example, the thickness of the functionally graded foam is in the form of steps when moving from the ends towards the centre.
In another embodiment, the pushrod may be filled with at least one volatile substance e.g., camphor or similar material. When the pushrod is driven at high speed, the temperature and duty cycle of pushrod would increase and therefore the volatile substance would form vapours. Vapours would exert vapour pressure i.e., increasing internal pressure while interacting with the foam, thereby further enhancing structural strength. For example, in a crash protection system, the increased internal pressure from the vapours reinforces the foam’s structure by expanding its porous matrix slightly boosting the load-bearing capacity of the structural member or pushrod 100.
In another embodiment, the structural member or pushrod may be filled with an inert gas or a volatile substance or a combination of both the inert gas and the volatile substance. The inert gases possess chemical stability and are non-reactive in nature enabling the structural member to maintain a consistent internal pressure reinforcing the structural integrity of the component, preventing deformation under stress or external loads. The non-reactivity of inert gases ensures that they do not corrode or chemically alter the surrounding materials, even in high-temperature environments, while their thermal stability allows them to perform reliably. Additionally, inert gases prevent oxidation and combustion, which is particularly beneficial in systems exposed to friction, heat, or high-speed movement. In dynamic applications, they can also act as a buffer, reducing friction and wear between moving parts. The combination of inert gases and volatile substance further enhances the load bearing capacity of the structural member or push rod 100. The combination of the inert gas and the generated vapours in a pushrod creates a synergistic effect by working together to improve both the load-bearing capacity and energy-dissipating properties of the component.
According to Fig. 9, the pushrod may accommodate both open-cell and closed-cell foams, allowing for design flexibility. The foam thickness can be tailored to the specific requirements of each application. In cases where functional grading is desired, the foam thickness can be varied strategically to achieve the desired performance characteristics. For example, as illustrated in in Fig. 9, the pushrod could be reinforced with varying foam thicknesses to optimize their respective functions.
Figure 10 illustrates a cross-sectional diagram of a drive shaft according to another embodiment of the present disclosure.
The drive shaft as depicted in Fig. 10 may be substantially similar to the structural member depicted in Fig. 6 and thus, the features common to both the drive shaft and structural member have not been repeated for the sake of brevity.
According to the embodiment of Fig. 10, the functionally graded foam may be an open cell foam or a closed cell foam extending across the elongated cavity of the drive shaft.
As can been seen in Fig. 10, the drive shaft 500 that has an open cell or a closed cell functionally graded foam includes a universal joints 502a, 502b at first and second end, reinforcing sleeves 504a, 504b at first and second end, and an outer sleeve 508. Further, the drive shaft may include uniform density or non-uniform density foam 506.
In an embodiment of the present disclosure, as shown in Fig. 10, the functionally graded foam is an irregular shaped foam having irregular wall thickness arranged or formed inside the drive shaft along the longitudinal axis.
In an embodiment of the present disclosure, the functionally graded foam of varying or irregular thickness may have a uniform density or a non-uniform density. In an example, as illustrated in Fig. 10, the thickness of the functionally graded foam is minimum or lowest at the ends e.g., a lower/first end and an upper/second end of the drive shaft while the thickness of the functionally graded foam is maximum at the centre. In another example, the thickness of the functionally graded foam progressively increases from the ends of the drive shaft towards the centre. In another example, the thickness of the functionally graded foam is in the form of steps when moving from the ends towards the centre.
According to Fig. 10, the drive shaft may accommodate both open-cell and closed-cell foams, allowing for design flexibility. The foam thickness can be tailored to the specific requirements of each application. In cases where functional grading is desired, the foam thickness can be varied strategically to achieve the desired performance characteristics. For example, as illustrated in in Fig. 10, the drive shaft could be reinforced with varying foam thicknesses to optimize their respective functions.

i. The present disclosure offers numerous advantages related to lightweight structural member. A few of the advantages achieved using the features of the present disclosure are provided below:
ii. The present disclosure provides a lightweight structural member with enhanced mechanical properties such as stiffness, strength and reliability.
iii. The present disclosure provides a lightweight structural member with enhanced strength-to-weight ratio that withstands high stresses without adding significant weight.
iv. The present disclosure provides a lightweight structural member that effectively mitigates noise, vibration, and harshness, ensuring a more comfortable and refined user experience.
v. The present disclosure provides a lightweight structural member that possesses higher natural frequencies, enhancing its stability and resistance to resonance.
vi. The present disclosure provides a lightweight structural member that possesses higher natural frequencies thereby enhancing its stability and resistance to resonance.
vii. The present disclosure is applicable to a wide variety of materials, metallic and non-metallic, both for the hollow structure as well as the foams.
viii. The present disclosure exhibits superior kinematic fidelity, enabling precise and accurate movement transmission.
ix. The present disclosure effectively resists buckling, ensuring structural integrity under compressive loads.
x. The present disclosure promotes greater system reliability by minimizing wear and tear, leading to reduced maintenance requirements and extended component lifespan.
xi. The present disclosure minimizes lubricant contamination due to wear debris, contributing to prolonged engine life and smoother operation.
xii. The present disclosure eliminates abrupt geometry changes, ensuring smooth stress distribution and structural integrity.
xiii. The present disclosure can be seamlessly integrated within the prevailing component design space without demanding additional space outside the component boundary.
The present disclosure provides a lightweight structural member that offers exceptional mechanical properties, reduced weight, and enhanced system reliability. The light weight of the structural member makes it versatile to get suited for a wide range of applications, including aerospace, automotive, construction, and seismic protection. The present disclosure accommodates both open-cell and closed-cell foams, allowing for design flexibility. The present disclosure provides a thin-walled structures of the structural member that may withstand significant compressive loads when pressurized. Further, for a pushrod, the disclosure also offers the advantage of minimal engine oil contamination due to wear debris, resulting in extended engine life and smoother operation. Moreover, the design eliminates abrupt geometry changes and can be seamlessly integrated within the prevailing component design space without requiring additional space outside the component boundary. The disclosure presents an innovative approach to enhance pushrod design, enabling improved performance even at higher engine speeds.
The light weight of the structural member finds applications in various fields, including but not limited to: Engine pushrods, including marine applications; Bicycle frames; Structural reinforcements; Motor cycle frames and handle bars; LCV chassis cross-members; Windmill and crane applications; reinforcement in robotic arms for better end-effector control; design of sacrificial structural members for protection against seismic activities; and space applications where strength-to-weight becomes a critical factor.
While the present disclosure has been described with reference to certain preferred embodiments and examples thereof, other embodiments, equivalents, and modifications are possible and are also encompassed by the scope of the present disclosure.

Dated this 06th day of February 2025

Sachin Manocha
[IN/PA-3247]
Of KRIA Law
Agent for Applicant
,CLAIMS:We claim:
1. A structural member (100) comprising:
an outer surface (102);
an inner surface (104);
an elongated cavity (106) extending along a longitudinal axis of the structural member (100);
a functionally graded foam (108) arranged within the elongated cavity (106) along the longitudinal axis, wherein the functionally graded foam (108) comprises an inner foam surface (118) and an outer foam surface (112); and
a layer (114) arranged between the inner foam surface (104) and the outer foam surface (112).

2. The structural member (100) as claimed in claim 1, wherein the functionally graded foam (108) is one of a metallic foam and a non-metallic foam.

3. The structural member (100) as claimed in claims 1 to 2, wherein the functionally graded foam (108) having varying densities is arranged within the elongated cavity (106).

4. The structural member (100) as claimed in claim 3, wherein the density of the functionally graded foam is minimum at a first end (116) and a second end (118) of the structural member (100), and wherein the density of the functionally graded foam (108) is maximum at a centre of the structural member (100).

5. The structural member (100) as claimed in claims 3 to 4, wherein the density of the functionally graded foam (108) progressively increases from the first end (116) and the second end (118) of the structural member (100) towards the centre of the structural member (100).

6. The structural member (100) as claimed in claim 1, wherein the functionally graded foam (108) with varying densities is continuously casted or formed within the elongated cavity (106) along the longitudinal axis.

7. The structural member (100) as claimed in claim 3, wherein the functionally graded foam (108) is an open cell foam.

8. The structural member (100) as claimed in claims 1 to 2, wherein the functionally graded foam (108) having varying wall thickness is arranged within the elongated cavity (106), and wherein the functionally graded foam (108) is at least an open cell foam or a closed cell foam.

9. The structural member (100) as claimed in claim 1, wherein the elongated cavity (106) is filled with an inert gas under a specified pressure to interact with the functionally graded foam (108).

10. The structural member (100) as claimed in claim 1, wherein the elongated cavity (106) is filled with at least one volatile substance to interact with the functionally graded foam (108).

11. The structural member (100) as claimed in claim 1, wherein the layer (114) comprises at least one of an adhesive material layer or a metal layer that facilitates attachment of the functionally graded foam (108) with the inner surface (104).

Dated this 06th day of February 2025

Sachin Manocha
[IN/PA-3247]
Of KRIA Law
Agent for Applicant