The leaf spring is frequently applied on a vehicle such as used on the truck and it is one of the machine element suspension systems. It needs to have an excellent resistance to the fracture propagation to avoid failure that could lead to severe accidents. Fracture failure on the leaf spring is frequently experienced especially on diesel trucks, known as premature failure. Therefore, this case is needed to be studied and investigated. The purpose of this study is to investigate the cause of failure on the broken leaf spring by counting analytically the stress intensity factor (KI) occurred near the crack tip. Moreover fracture surface observation conducted by Scanning Electron Microscope (SEM) to find out whether there is or not an initial crack and crack propagation direction. This present study describes the experimental work and analytical analysis of theleaf spring used on Diesel Truck Vehicle. Hardness testing was performed using the Rockwell method. The chemical composition testing on the leaf spring material was found that the material in accordance with AISI 5150 standard. The hardness value of leaf springs tested of about 106.9 HRB. The result of analytical analysis shows that the maximum value of stress intensity factor (KI) occurred near the crack tip at the near the hole of leaf spring. In this case the value of KIis higher than thevalue of the fracture toughness (KIC) of the leaf spring material. Therefore, this result could be inferred that crack propagation happened starting from initial crack tip which is located near the hole on the leaf spring. The failure of leaf springs also caused by fatigue crack propagation due to dynamic loading during the operation marked by appearance the beach mark on the fracture surface.

Damage is often experienced by leaf springs of diesel trucks, known as premature failure and is need to be analyzed. Thus, this study aims to analyze the causes of failure of leaf springs through analytical and numerical analyses. Hardness testing was performed using the Rockwell method. Microstructure was observed using scanning electron microscopy to identify the fracture surface. Analytical and numerical analyses were used to obtain the load distribution of each spring. The analysis results of load distribution on each spring were 26.95 kN. The chemical composition of the specimen shows that the material was tested according to AISI 5150 standard. The hardness value of leaf springs tested was HR_B 106.9. The Result of numerical and analytical shows that the strain, stress and deformation of leaf springs with maximum values occurred at the near of hole of spring. The K _I value ≈ K_IC , therefore this may cause crack propagation. The failure of leaf springs was caused by fatigue during the operation marked by a beach mark and the normal stress is far below the specimen fatigue strength.

In this paper, the authors have discussed the extraction of the fatigue features for the strain signal with the help of the Morlet wavelet. When the time domain signal is transformed into a time-frequency domain, it displays the signal energy distribution regarding the specific time and frequency data. Here, lower amplitudes present in the primary signal get eliminated due to their energy and a new short signal gets generated. According to the simulation results, the Morlet wavelet could shorten the initial signal length by approximately 70 % and retain 91 % of the primary fatigue damage. With the help of the edited and shortened strain signals, there was a 69.5 % decrease in the time needed to carry out the fatigue test. Therefore, the data which summarizes the computational algorithm could accelerate the fatigue testing. In conclusion, this method can be used as a good alternative method for studying the fatigue durability, particularly in the field of automotive engineering.

A pulley is a mechanism consisting of a wheel, with a groove between its two edges, which is fastened to a shaft. The belt usually passes along the groove of the pulley to give it the power of movement and rotation. In December 2016 there was a case of failure of the crankshaft pulley in a truck. This study aims to investigate the causes of fracture. Therefore, it was necessary to perform a failure analysis. Investigation methods included visual examination, scanning electron microscope analysis, chemical analysis of the material and mechanical tests. A finite element analysis (FEA) was also performed to quantify the stress intensity factor (K_I) distribution in the crankshaft pulley that is near the crack tip. From the finite element analysis, it was found that K₁ was greater than the fracture toughness (K_IC) of the material. Therefore, the propagation of crack occurs from the initial crack until final failure.

This paper aims to characterize strain signals acquired at an automotive coil spring. The strain signals were caused by vibrations of the tire while the car was being driven on various types of road surfaces at different speeds. The rural road gave high amplitudes containing spikes when the tire touched a curb, bump or pothole. These conditions contributed to a higher loading rate to the car component, contributing to shorter useful life, which was 1,926, 1,574 and 1,401 reversals of blocks for the Coffin-Manson, Morrow and SWT models, respectively. Driving on the rural road resulted in a 6-times and 8-times decrease in the useful life of the coil spring in comparison to the urban and the highway roads, respectively. In conclusion, the rural road caused stronger vibrations to the component because it has a rough surface; meanwhile, the highway road provided lower vibrations because the road was smooth. Damage due to fatigue increases with the vibrations subjected to a component leading to fracture.

Steel construction is mostly connected by using a welding technique. The result of the welding process can cause the change of mechanical properties of the welding zone. Therefore, it needs to be reviewed to guarantee the quality of the welding zone. This research aims to assess the effect of welding on the change of microstructure and the mechanic characteristic of welded connection. Low carbon steel was welded by using Shield Metal Arc Welding method (SMAW) with electrode E7016, diameter 2,6 mm. Type of notch used was single V with angle 70° and welding position was 1G. Then, the Charpy impact test, Rockwell hardness and micro-macro structure monitoring on the welding zone including base metal, Heat Affected Zone (HAZ) and weld metal, are conducted. The results show that the highest impact toughness value at metal welding area is 251 joule/mm², and lowest impact toughness is at the heat affected area (HAZ) is 119 joule/mm². Hardness values of welding zones are found of about 87,6 HR_B for weld metal, 73,9 HR_B for HAZ zone and 67,1 HR_B for the base metal. The microstructure of weld metal zone, HAZ and base metal are included on ferrite and pearlite formed by welding on low carbon steel AISI 1010 observer by using an optic microscope.