Papers by Keyword: Impact Testing

Abstract: The human skull can become fractured or injured through impact and often requires repair through a craniectomy and subsequent cranioplasty, surgery performed to repair defects or damage to the cranium. Challenges related to material choice, which must be biocompatible, and customization for each patient’s anatomy remain. One possible solution is fabrication of patient-specific cranial implants, out of biocompatible polymers, using single point incremental forming (SPIF). In this paper, polyetheretherketone (PEEK) and ultra-high molecular weight polyethylene (UHMWPE) are formed using SPIF at room temperature to manufacture a cranial implant. The SPIF process is used to produce formed parts from which test specimens were extracted to evaluate the tensile performance and thermal properties. Formed cranial implants were impacted using a drop weight to evaluate their suitability under relevant conditions. The geometric conformance of the SPIF process was studied to compare the material behavior for the specified polymers after forming. The results validate that SPIF can be conducted at room temperature with PEEK and UHMWPE biocompatible polymers to enable custom implant manufacturing. However, PEEK exhibited superior performance in terms of tensile strength, geometric conformance, energy absorption, and melting temperature, and is recommended over UHMWPE for future implant applications.

Abstract: This study is carried out to investigate the ductile to brittle fracture behavior of special high strength low alloy steel (HSLA), which is used in aerospace applications. As aerospace materials are subjected to temperature variations during their actual use therefore it is very important to know their fracture behavior with change of temperature. Alloy having 0.3 %C, 0.88 % Mn and 1.0% Si was heat treated to obtain tempered martensite and ferrite and tempered martensite structures. Impact toughness tests were carried out at temperature range from – 60 °C - 200 °C in as received, fully quenched, and tempered and quenched and tempered in two phase (a+ γ) state. Then the effect of different heat treatments on impact transition temperature was studied.

Abstract: This paper presents a new method based on the split Hopkinson pressure bar (SHPB) to perform impact combined shear-compression test for cellular materials. For this purpose, a bevelled end is cemented to the input bar and the output bar are rotatable to be parallel to the inclined plane of the bevelled end. The system uses the friction between the specimen and the pressure bars to apply the combined shear compression loading on the honeycomb specimen. Such a testing method is validated by the simulation of the whole loading system (split bar + specimen) using ABAQUS code. It shows that this combined shear-compression test provides a quite accurate measurement. Tests on the 5052 aluminium honeycombs are performed. The shear stress-strain behaviour and the compressive behaviour are separated. The experiment result confirms previous testing results and reveals that the shear component will weaken the compressive strength of the honeycomb at high strain rate.

Abstract: Investigation of impact damage on advanced composite materials of Carbon Fiber Reinforced Epoxy (CFRE) composites and Glass Fiber Reinforced Epoxy (GFRE) composites under high strain rate impact load have been conducted in the present study. Four types of GFRE plates were studied after being impacted with various thicknesses and fixed impact parameters. Results of the present experiments were characterized by the comparison of damage zone among CFRE/GFRE, GFRE with honeycomb core and GFRE without honeycomb core. The result suggests that CFRE is the better structure than GFRE under low velocity impact loads. Higher energy needed to damage the surface of GFRE with core compared to GFRE without core plates.

Abstract: Finite-element (FE) analysis is important instrument for prediction of plastic car bumper tests. Accuracy of FE analysis depends on accuracy of material input data. It has developed experimental methodology for identification of mechanical properties. The methodology leads to more accurate material input data for numerical simulations.

Abstract: Thermoplastic composite manufacturing is often difficult due to high viscosity of the matrix materials. Coupling a high level of mechanical properties with simple, low-cost processing technique is a difficult subject, but an important task for any state-of-the-art impregnation processes. In this paper, Thermoplastic Prepreg Fabrication Technology is utilized to prepare thermoplastic tapes and the technology's effect on strain energy absorption was investigated. The tape was prepared under three categories: first, with induced vibration and no fiber preheat (NV), second, without vibration and fiber preheat (HN) and last, with both fiber preheat and vibration (HV). For the purpose of comparison, all other variables such as pulling speed, fiber tension, fiber preheat and processing temperature were kept constant. The HV category showed improvement in the strain energy absorption by 10 and 23% when compared to HN and NV, respectively. In addition, HV had better wetting, fiber spread and dispersion. Fiber preheating is important as it worked well with vibration possibly due to good fiber spread on the HV category (widest tape). Also, HV had the least fiber volume fraction as it takes more matrix volume when exiting the die plate.

Abstract: Milling is one of the most common manufacturing processes for automotive component, but its productivity is limited by chatter. This form of chatter is undesirable because it results in premature tool wear, poor surface finish on the machined component and the possibility of serious damage to the machine itself. Modal testing is a form of vibration testing which is able to determine the Frequency Response Function (FRF) of the mechanical test structures. In this paper, the main focus is to obtain natural frequency values for machine tool components in order to establish better conditions in the cutting process on the machine tool. For this purpose, a 3D model of the machine tool’s part is made using design software and exported to analysis software. Later on, the Finite Element Method (FEM) modal analysis was used to obtain the natural frequencies. The model is evaluated and corrected through an experimental modal test. In the experiment, the machine tool vibration is excited by impact hammer and the response of excited vibration is recorded. In the end, the result of both FEM and experimental shows a good consistency in comparison.

Abstract: Vibration based technique have so far been focused on the identification of structural damage. However, not many studies have been conducted on the corrosion identification on pipes. The objective of this paper is to identify corrosion on pipes from vibration measurements. A hollow pipe, 500 mm in length with 63.5 mm in diameter was subjected to impact loading using an impact hammer to identify the natural frequency of the tube in two conditions i) without any corrosion and ii) with an induced localized 40 mm by 40 mm corrosion at the middle of the pipe. The shift of natural frequencies of the structures under free boundary conditions was examined for each node of excitation. The results showed that there is a shift in natural frequency of the pipe, between 3 and 4 Hz near to the corrosion area. It can suggested that that the impact vibration is capable of identifying of localized corrosion on a hollow tube.

Abstract: Article deals with construction of hammer for cane shredder. Function of hammer in shredder consists in crushing sugarcane stalks for further processing in sugar production. Hammer loading and other calculations were made. Four weld deposit materials were suggested for protection of hammer against wear and dynamic loading. All samples with weld deposit were subjected to microstructure evaluation, chemical analysis, high speed impact testing and tribological PIN-on-DISC test for estimation of wear resistance. One weld deposit material was recommended as a result of these tests.

Abstract: Modal experiments are present to study dynamic behaviors of an external prestressed steel beam. The impact testing is introduced, when the input is fixed and FRFs are measured for multiple outs. Modal results indicate that the modal shape will increase when external prestressed load exists; the first order frequency of external prestressed load on the beam is higher than that of no load, but the amount of loads have little influence on the value of damping coefficients and the first order frequency; and there are denser frequencies with lager external prestressed load.