Can the dynamic amplification factor (DAF) for instantaneously loaded structures be larger than 2? When assessing alternative load paths in structures subjected to instantaneous column loss, DAF = 2 has long been regarded as a conservative upper boundary. In our new paper in Engineering Structures by Alex Sixie Cao, Pedro Palma, and Frangi Andrea, we provide the first analytical proof to demonstrate the dependency of the DAF on the mechanisms developing in the system, which could lead to DAF > 2. What this means: 🏗 In beam-column assemblies with sudden column loss, the DAF depends on the load-carrying mechanism. With elastic tensile catenary action, values can reach up to 4. 💥 Under impact with initial velocity (falling debris, vehicles, rock/icefall), the DAF has no upper bound and grows with the ratio of drop height to displacement.   📏 Some design standards may underestimate dynamic effects, as they combine incompatible assumptions about structural response and loading pulse shapes. Why it matters: ⚠ The assumption of an upper limit of DAF = 2 may not be conservative and may underestimate dynamic effects.    🛠 The load-carrying mechanism must be engineered carefully to reduce dynamic effects. 📏 Incompatible assumptions about the structural response and loading pulse shapes may underestimate dynamic effects. Full article: https://lnkd.in/ebe5Tk_R

Engineering Note: Real-World Lessons from Transportation Vibration Analysis Transportation analysis is often treated as an afterthought - done late in the design cycle or sometimes skipped altogether in the hope that everything will “just work out”. But when equipment is shipped over long distances, especially with unique configurations, overlooking vibration loading can lead to costly failures. I recently wrapped up a consulting project involving ground transport of a large modular structure - essentially a container sized frame with multiple heavy fan units suspended from its sides. While similar units had been shipped before, this was the first time with fans mounted in that configuration, prompting a deeper analysis. Following MIL-STD-810H, the go-to standard for dynamic environments in air, rail, and ground transport, we ran a Random Vibration analysis. Early results showed negative stress margins around key locations - especially concerning since the suspended subassemblies had a natural frequency around 25 Hz, right where excitation is significant. We then explored less conservative vibration profiles: ·        ASTM D4169 gave some margin improvement, ·        But switching to ISTA 3H, suitable for Air Ride trucks, made a substantial difference. The comparison between MIL-STD-810 and ISTA 3H shows over a 10 dB reduction in the excitation spectrum near 25 Hz. That shift, combined with the fact that the first mode dominated mass participation, translated (via the Miles Equation) into a threefold reduction in stress. With this approach validated through full Random Vibration simulation, we turned negative margins into acceptable ones and cleared the structure for shipping via Air Ride trailer. A great technical reference comparing test profiles can be found in this paper: 🔗 https://lnkd.in/gJ3jMFPC This is a reminder of how critical it is to pair practical experience with the right simulation tools and to start transportation analysis early when possible. #Engineering #FEA #VibrationAnalysis #MILSTD810 #TransportationEngineering #StructuralDynamics #Consulting #FiniteElementAnalysis

Modal Analysis is an important aspect of the mechanical engineering field of structural dynamics. It plays an important role in product development as well as vibration and stress problem-solving. This guide focuses on the experimental testing aspects of modal analysis providing an overview of the basic principles and methods involved. This guide is ideal for: Engineers in mechanical, aerospace, automotive, civil, and structural disciplines R&D teams conducting vibration testing or product design optimization Graduates & researchers working with structural dynamics or FEA validation Click the button below to request your copy! https://lnkd.in/grMG8QRg 6D Testing and Analysis #ModalAnalysis #MechanicalEngineering #Testinng #TestAndAnalysis #ExperimentalModalAnalysis

Engineering Note: Real-World Lessons from Transportation Vibration Analysis Transportation analysis is often treated as an afterthought - done late in the design cycle or sometimes skipped altogether in the hope that everything will “just work out”. But when equipment is shipped over long distances, especially with unique configurations, overlooking vibration loading can lead to costly failures. I recently wrapped up a consulting project involving ground transport of a large modular structure - essentially a container sized frame with multiple heavy fan units suspended from its sides. While similar units had been shipped before, this was the first time with fans mounted in that configuration, prompting a deeper analysis. Following MIL-STD-810H, the go-to standard for dynamic environments in air, rail, and ground transport, we ran a Random Vibration analysis. Early results showed negative stress margins around key locations - especially concerning since the suspended subassemblies had a natural frequency around 25 Hz, right where excitation is significant. We then explored less conservative vibration profiles: ·        ASTM D4169 gave some margin improvement, ·        But switching to ISTA 3H, suitable for Air Ride trucks, made a substantial difference. The comparison between MIL-STD-810 and ISTA 3H shows over a 10 dB reduction in the excitation spectrum near 25 Hz. That shift, combined with the fact that the first mode dominated mass participation, translated (via the Miles Equation) into a threefold reduction in stress. With this approach validated through full Random Vibration simulation, we turned negative margins into acceptable ones and cleared the structure for shipping via Air Ride trailer. A great technical reference comparing test profiles can be found in this paper: 🔗 https://lnkd.in/gWuEg4xk This is a reminder of how critical it is to pair practical experience with the right simulation tools and to start transportation analysis early when possible. #Engineering #FEA #VibrationAnalysis #MILSTD810 #TransportationEngineering #StructuralDynamics #Consulting #FiniteElementAnalysis

Date: 08 / 10 / 2025 Topic: Static Frictional Force By: NIP 📚 📌📌Static frictional force is the force that opposes the initiation of motion between two surfaces that are in contact with each other. It is a type of frictional force that acts when an object is stationary and prevents it from moving. 📌📌Key Characteristics 1. Prevents motion: Static friction prevents an object from moving when a force is applied. 2. Maximum value: Static friction has a maximum value, known as the limiting static friction. 3. Dependent on surface: Static friction depends on the nature of the surfaces in contact. 📌📌Formula Fs ≤ μs × N Where: Fs = static frictional force μs = coefficient of static friction N = normal force (perpendicular to the surface) 📌📌Important Points 1. Static friction is self-adjusting: It adjusts its magnitude to match the applied force. 2. Static friction is not constant: It can vary from 0 to its maximum value. 📌📌Applications 1. Traction: Static friction provides traction, allowing objects to accelerate or brake without slipping. 2. Stability: Static friction helps maintain stability, preventing objects from sliding or toppling. 📌📌Example A book on a table will not move unless a force greater than the static frictional force is applied. Once the book starts moving, kinetic friction takes over.

Every rotating machine must operate away from its structural natural frequencies to ensure long-term reliability and vibration-free performance. This study focuses on the dynamic evaluation of a motor frame and its coupling frame under operational conditions. Through finite element analysis, the natural frequencies were compared against the machine’s operating speed to ensure adequate separation from critical harmonics.

The #1 Mistake in Choosing Thermal Grease High thermal conductivity (TC) is important, but it's not the whole story. The real enemy of performance is high thermal resistance. Here’s why: ➡️ TC is the material's potential to conduct heat. ➡️ Resistance is the actual barrier to heat flow at the interface. Even a high-TC grease can fail if it pumps out, dries, or doesn't spread thin enough to eliminate air gaps. The solution? Focus on application performance: ✔️ Low Pump-Out: Stays put under thermal cycling. ✔️ Optimal Viscosity: Spreads easily for a thin Bond Line Thickness (BLT). ✔️ Long-Term Stability: Performs consistently for years. At (CAYOM), we engineer for low interfacial resistance, not just a high number on a datasheet. What's more critical in your design: peak thermal conductivity or long-term stability? #ThermalManagement #ThermalGrease #TIM #ElectronicsCooling #Engineering #HeatSink #Reliability #PCB #HardwareDesign #ThermalPerformance

The #1 Mistake in Choosing Thermal Grease High thermal conductivity (TC) is important, but it's not the whole story. The real enemy of performance is high thermal resistance. Here’s why: ➡️ TC is the material's potential to conduct heat. ➡️ Resistance is the actual barrier to heat flow at the interface. Even a high-TC grease can fail if it pumps out, dries, or doesn't spread thin enough to eliminate air gaps. The solution? Focus on application performance: ✔️ Low Pump-Out: Stays put under thermal cycling. ✔️ Optimal Viscosity: Spreads easily for a thin Bond Line Thickness (BLT). ✔️ Long-Term Stability: Performs consistently for years. At (CAYOM), we engineer for low interfacial resistance, not just a high number on a datasheet. What's more critical in your design: peak thermal conductivity or long-term stability? #ThermalManagement #ThermalGrease #TIM #ElectronicsCooling #Engineering #HeatSink #Reliability #PCB #HardwareDesign #ThermalPerformance

Call for Papers: Sound & Vibration Sound & Vibration is an international peer-reviewed journal dedicated to advancing knowledge and promoting innovation in all areas of sound and vibration. Topics include, but are not limited to: ✅ Broad-based interests in noise and vibration ✅ Dynamic measurements ✅ Structural analysis ✅ Computer-aided engineering ✅ Machinery reliability ✅ Dynamic testing For detailed author guidelines and to submit your paper, please visit: https://lnkd.in/gCu548Zb #CallforPapers #SoundAndVibration

Research on the Nonlinear Confined Buckling Pressure of a Thin-Walled Metal Liner with an Ovality Defect Installed Inside the #Composite Overwrapped Pressure Vessels by Fuwei Gu et al. J. Compos. Sci. 2025, 9(9), 480; https://lnkd.in/dgiivN2U Abstract Composite overwrapped pressure vessels (COPVs) have become the core unit for high-pressure hydrogen storage and transportation. However, excessive autofrettage pressure could induce unilateral buckling damage of the metal liner because of large rebound compressive stress induced by large plastic deformation in the depressurization stage. When the liner contains initial defects, its critical unilateral buckling pressure would be further reduced. In this paper, a critical buckling pressure calculation formula was established by finite element analysis and theoretical derivation. Firstly, the classical theoretical calculation models and research methods were analyzed and discussed. Then, by discussing the key influencing parameters, a semi-empirical calculation formula of nonlinear confined buckling pressure of a metal liner with ovality defects was established. Finally, the proposed semi-empirical formula was used to predict the critical internal pressure of a Type-III COPV, and the predicted value was compared with the experimental result. The predicted result was higher than the experimental result and the error range was −2.8%~−23%. The proposed semi-empirical formula of nonlinear confined buckling could provide theoretical support for designing the autofrettage pressure of Type-III COPVs and help to reduce the uncertainty and repeated test cost in the design process. Keywords: COPVs; thin-walled metal liner; nonlinear confined buckling; elastic buckling; ovality defect; #finite #element #analysis