Decrease In Impact Energy Research Articles

Effects of impact angles and shapes on CAI strength of composite honeycomb structure

The Compression After Impact (CAI) strength can enhance safety and reliability in engineering applications, improve simulation and prediction capabilities. It is also an important indicator for assessing the damage tolerance capacity of composite structures. The CAI strength is directly influenced by low-velocity impact, which holds significant scientific research implications for evaluating structural safety, optimising design and enhancing material properties. Analysing different impact shapes and angles provide a closer representation of real-world engineering scenarios, rendering results more reliable and valuable. The subject is a CFRP panel with Nomex honeycomb sandwich structure, where both the skin and core are composed of composite materials. Low-velocity impact and compression after impact tests were conducted to establish an integrated and refined finite element model for the CFRP panel with Nomex honeycomb structure. The model’s validity was confirmed by comparing with test results. Various impact shapes and angles were investigated using the established model to examine their influence on the CAI strength of the composite honeycomb sandwich structure. The following conclusions were drawn: (1) Sharper impactors result in lower CAI strength and higher compressive failure displacement. (2) The CAI strength, normalised CAI strength, and failure displacement of the structure increase with the impact angles. Among the tested angles, the 30° impact angle induced the least damage, exhibiting the highest CAI strength, normalised CAI strength, and failure displacement. However, as the angle increases, energy losses between the impactor and specimen increase, impact energy decrease. Consequently, the structural indicators decrease compared to the 30° impact angle.

Strength, durability, and impact behavior of recycled aggregate concrete with polypropylene aggregate

Massive consumption and production of plastic is expected to have a significant environmental impact in the near future. Plastic waste from landfills can be refined and recycled as aggregates in concrete through subsequent processing. Several studies have already been conducted using plastic scraps as aggregate in concrete. However, more research is needed before it can be incorporated into structural concrete. Therefore, this study aims to investigate the static and dynamic behavior of concrete made with polypropylene plastic aggregate (PPA) obtained from waste plastic materials. Natural coarse aggregate (NCA) and recycled concrete aggregate (RCA) are partially replaced with PPA in this study and drop impact tests are performed after the samples are exposed to room and elevated temperatures (200 °C and 400 °C). PPA replacement percentages are 0, 5, 10, and 15 %. The drop impact test is performed on both cylinders (150 mm × 63.5 mm) and beams (100 × 100 × 500 mm) specimens. Different mechanical and durability tests are also investigated. The impact energy decreases by up to 68 percent as the PPA percentage increases at room temperature. Furthermore, when the specimens are heated to 200 °C or 400 °C, the impact blows are significantly reduced (6–13 no). After being heated to 200 °C and 400 °C, the 15 percent NCA replaced cylinder loses 87 percent and 91 percent of its impact energy, respectively. In terms of mass loss, the control cylinder has a higher loss than the PPA cylinders, indicating that the presence of PPA in concrete causes less damage. In terms of mechanical properties, the 5 percent PPA-based concrete outperforms the control. Depending on the concrete age and coarse aggregate types, a 5 % PPA content increases compressive strength by up to 11.6 percent. In terms of durability, the water absorption tendency increases with increasing PPA content, and all-natural PP concrete (NPC) and recycled PP concrete (RPC) exhibit moderate to very low chloride ion penetrability. Overall, it is proposed that 5 % PPA be used with NCA and RCA for structural applications.

Insights into the dynamic impact behavior of intercritically annealed automotive-grade Fe–7Mn–4Al −0.18C steel

Recently, medium manganese steels (MMnS) have been developed due to their excellent strength and improved ductility to meet automotive manufacturer demands. However, research on the impact toughness of automobile parts developed from these steels needs considerable attention to meet safety standards. Therefore, the present investigation focuses on the effect of annealing time (30, 60 and 180 min) on the impact behavior of intercritically annealed (750 °C) Fe–7Mn–4Al-0.18C (wt. %) steel. The microstructure of intercritically annealed steel, as revealed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), consists of blocky and lath-type reverted austenite (RA), fine intercritical ferrite (IF), lath-type martensite (M) and coarse elongated ferrite (EF). The impact toughness of the samples is evaluated at room temperature using a Zwick/Roell HIT450P Charpy impact machine. The sample annealed for 60 min absorbs the highest amount of impact energy among the three annealed samples. This is due to an increased volume fraction of RA, the transformation-induced plasticity (TRIP) effect, and an increase in the fraction of high angle grain boundaries (HAGBs). The microtexture analysis reveals that the presence of γ-fiber {111}//ND texture in ferrite and Rotated Goss texture {011} <011> in austenite contributes to the improved impact toughness in the specimen annealed for 60 min. The SEM fractographs of the sample annealed for 60 min exhibit crack branching and larger dimple size with inhomogeneous dimple distribution indicating higher energy absorption during crack initiation. Martensitic transformation nucleation sites are activated by a high volume fraction of RA in the sample annealed for 60 min, leading to increased impact toughness and the development of secondary cracks. In addition, the impact energy decreases when the sample annealed for 60 min is subjected to an impact test at temperatures lower than room temperature.

Effect of thermal aging on the microstructure and mechanical property of 410S ferritic stainless steel

The low chromium ferritic stainless steel, 410S, as a candidate control rod drive mechanism (CRDM) material used in nuclear power plants, was subjected to accelerated thermal aging at 400 °C in air up to an exposure period of 10,000 h (∼417 days). A series of analytical techniques including optical microscope (OM), electron back scatter diffraction (EBSD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and 3D atom probe tomography (3D-APT) were used to characterize the evolution of the microstructure with thermal aging time, whilst a couple of tests (i.e., hardness, Charpy impact and tensile tests) were employed to link the changes of mechanical properties at different thermal aging times with the microstructure. After ≤3000 h thermal aging treatment, Cr-rich α′ phase formed near the ferritic grain boundaries, leading to minor change in the hardness and strength of 410S but sharp decrease in impact energy. When the thermal aging time increased to 10,000 h, the formation of Cr-rich α′ phase spread from near the ferritic grain boundary to the inside of ferritic grain and the growth of carbides precipitated led to the slight increase in the hardness and strength but the decrease in the impact energy and plasticity. Under these circumstances, the decrease of free substitutional atoms (i.e., Cr) caused by the formation of Cr-rich α′ phase and the growth of carbides changed the dynamic strain aging type from type B to type A.

Effect of coiling temperature on the structure and properties of thermo-mechanically rolled S700MC steel

The boron-free S700MC steel is usually produced by exploiting the properties of a ferrite-bainite mixed microstructure formed by coiling the strips at a temperature of about 450?C, i.e.below the bainite starting temperature. With the aim of further enhancing the mechanical properties of 6 to 10 mm thick strips, industrial tests were carried out at a coiling temperature of 600?C to promote the formation of a structure of ferrite and carbides, which is also acceptable for this type of steel. Unexpectedly, a microstructure composed of ferrite and martensite was obtained. Compared to the ferritic-bainitic grade, the new structure is characterized by a slight decrease of the yield point but by an increase of the ultimate tensile strength by no less than 80 MPa, with a transition from a quasi-discontinuous to a clearly continuous yielding behaviour. Accordingly, the ratio of yield strength to tensile strength decreases from 0.90 to 0.75 and the impact energy decreases by 35 J and 60 J for the two gauge levels, respectively. The mechanical behaviour of the strips coiled at high temperature is explained as a direct consequence of the dual phase structure with a hard phase interspersed in a soft ferrite matrix. The presence of martensite is explained by the so-called incomplete bainite reaction. The partial transformation into ferrite after coiling and the long time required for the coil to cool down stabilize the untransformed austenite due to the carbon enrichment making bainite formation at lower temperatures impossible.

The impact-abrasive wear behavior of high wear resistance filling pipeline with explosion treatment

This work investigated the effect of explosion treatment on the wear resistance of Fe-31.6Mn-8.8Al-1.38C steel and the impact-abrasive wear behavior. The results show that under the different impact energy (1, 2 and 4 J), the wear resistance of the experimental steel after explosion treatment is improved by 1.32–1.40 times compared with that without explosion treatment, the hardness and the work hardening rate are also increased. The wear surface mainly consists of furrows and delaminated craters, as well as some cracks and press-in abrasives. With the decrease of impact energy, the furrows are deeper and longer gradually. The delaminated craters and press-in abrasives increase with the increase of cracks. During impact-abrasive wear, the work hardening occurs again on the surface with explosion treatment, and the work hardening of the wear surface is attributed to the generation of dislocations, mainly the microband induced plasticity (MBIP) effect, which improve the wear resistance.

Effect of helical rolling on the bainitic microstructure and impact toughness of the low-carbon microalloyed steel

Ferrite-bainite microstructures and impact toughness of the X65 low-carbon microalloyed steel were investigated after helical rolling at 1000, 920, 850, and 810 °C followed by continuous cooling in air. After helical rolling at 1000 °C, granular bainite with large areas of the massive-shape martensite-austenite constituent (d = 1.5 μm) and a high fraction of twinned martensite (d > 2.0 μm) were observed in the steel. This caused a decrease in impact energy at low test temperatures (for example, 70 J at –70°С). Lowering the helical rolling temperature contributed to a reduction of dimensions of both ferrite-bainite and martensite-austenite constituent areas, as well as the replacement of the latter by a slender type one and an improvement in fracture toughness at the low temperatures. The highest impact energy level (210 J at –70 °C) was achieved after helical rolling at 850 °C due to the formation of a homogeneous microstructure, which included dispersed ferrite grains, granular bainite and small fractions of the slender type martensite-austenite constituent (d = 0.1–0.7 μm). In this case, areas of twinned martensite were absent.

Life cycle energy (LCE) on project life cycle (PLC): a literature review

Construction activities gradually consume energy during their life cycle, namely material extrusion, transportation, production, assembly line, installation, demolition and disposal. This research aimed to identify research about energy such as embodied and operational energy. Operational energy is energy that is used during building life cycle to decrease global warming effect. This research used a qualitative method to identify and review some literature related to decreased energy construction. This study showed that 98% of researchers focus on energy efficiency in the design, construction and operational stages. Only 2% were investigating at the initiation stage. Some recommendations can be drawn suggesting that energy reduction is possible by applying optimization strategy to all project life cycle (PLC). Initiation and design phase are indirect energy optimization phase through policies and design buildings, which significantly impact energy decrease for further phases. In contrast, construction and operations phase is direct energy optimization phase through energy efficiency on each activity.

Effect of Deformation Parameters on Microstructure and Mechanical Properties of Internal Crack Healing in As‐Cast 30Cr2Ni4MoV Steel

Crack defects seriously affected the quality of heavy forgings, which needed to be eliminated by forging process. In this study, the healing process of internal crack defects was studied under different deformation parameters. The internal crack was produced by drilling the sample of 30Cr2Ni4MoV steel and then compressing the sample with different deformation. The microstructure of the crack healing zone was observed using an optical microscope. Meanwhile, the static and dynamic mechanical properties of the crack healing zone were tested by room‐temperature tensile tests and impact tests, respectively. The results showed that dynamic recrystallization (DRX) and grain growth were the main factors for internal crack healing. When the forging ratio (FR) was 1.5, the cracks at the corner of the void began to heal, which was caused by DRX. At FR 2.0, the DRX was completed and the center crack was completely healed. The tensile properties of crack healing zones were restored to more than 95% of the base material. As the FR increased to 2.2, the elongation increased slightly and the yield strength decreased slightly, which indicated that the grain growth played an important role in the plastic recovery and DRX played an important role in strength recovery. The dynamic mechanical properties of the crack healing zone gradually increased with the increase of deformation. Furthermore, the maximum value of impact toughness reached FR 2.0, and the recovery rate of impact toughness was above 96%. When the deformation continues to increase, the grains grew up after DRX, which made the impact energy decrease.

Long-term thermal aging performance of welding structures in primary coolant pipes for nuclear power plants

Welding structures of primary coolant pipes were subjected on a series of accelerated thermal aging test at 400 °C until 30,000 h to investigate the resulting microstructure, impact and nanoindentation properties change. The results indicated that after long-term thermal aging, a mottled structure and precipitated G-phases were observed in ferrite phases both of straight pipes and welded joints, leading to a decrease in impact energy and an increase in nanohardness. Moreover, until thermal aging saturation, impact energy of welding structures was still higher than initial design value (80 J), thus demonstrating a high toughness reserve, but saturated impact energy in welded joints was higher than that in straight pipes owing to lower ferrite content. Furthermore, there were higher-density spinodal decompositions and more precipitated G-phases in welded joints than those in straight pipes owing to micro-defects generated from welding process, resulting in a higher nanohardness in ferrite phases of welded joints.

Optimization of shielding gas composition in high nitrogen stainless steel gas metal arc welding

Abstract High nitrogen stainless steel has extensive applied foreground in industries. But the weldability limits the use of the steel. The weld without nitrogen can become the weakness of the joint in corrosion resistance and strength. In this study, response surface methodology was applied to optimize the Ar-N2-CO2 ternary shielding gas for a nitrogen-containing filler metal in high nitrogen stainless welding. The influence of the proportion of N2 and CO2 on the nitrogen content, the impact energy and the tensile strength were investigated by the statistical regression models. The results show that the tensile strength, nitrogen content and impact energy increase and then decrease with the increasing of CO2, which indicates that CO2 content should not be too high. N2 addition can increase the nitrogen content of the weld obviously. But the impact energy decreases when N2 content exceeds about 7%. Integrating the mathematic models of the three performances, the optimal shielding gas compositions were determined to be 87 %Ar-6.5 %N2-6.5 %CO2. With this optimal shielding gas, the tensile strength and impact energy reached 956.7 MPa and 166.8 J, respectively. The deviation between the experimental value and the predicted value was below 2%.

Numerical Simulation, Microstructure, properties of EH40 ultra-heavy plate under gradient temperature rolling

This paper investigates the novel gradient temperature rolling process for ultra-heavy plates. Between rolling passes, water cooling is used to create a temperature gradient along the thickness direction of the ultra-heavy plate, which increases deformation of the core and improves the final mechanical properties of the plate. The DEFORM-3D software package was used to simulate the temperature and strain fields of the gradient temperature rolled plate. Simulation results show an obvious temperature gradient along the thickness direction of the plate and during rolling, deformation is more likely to penetrate the core. The surface to core strain ratio decreased from 14.7:1 to 1.8:1 compared to conventional rolling. Furthermore, the results of hot rolling experiments clearly show refinement of the microstructure. A layer of fine grains with an average diameter of about 1–2 μm formed on the surface of the plate and the average grain size was found to be 6.7% finer at 1/4-thickness and 11.8% finer at 1/2-thickness compared to conventionally rolled sheets. Moreover, the high-angle grain boundaries were 8.7% larger at 1/2-thickness. The microstructure of the gradient temperature rolled plate is mainly ferrite and pearlite with a small amount of granular bainite at the core. The pearlite phase initially exhibits a lamellar structure that is eventually transformed into degraded pearlite. The granular bainite is finer and more uniformly distributed compared to that of a conventional rolling plate. In addition, the yield strength and tensile strength of the gradient temperature rolling plate are higher and less elongation is observed, and the impact energy at low temperatures (−20 °C and −40 °C) is higher; from the surface to the core as the thickness increases, the decrease in impact energy is even smaller.

Effect of Cu and Mo addition on mechanical properties and microstructure of grey cast iron: An overview

The addition of any alloying element alters the various properties of developed alloy, wherein mechanical properties influence significantly. The present work reviews the effect of molybdenum (Mo) and copper (Cu) addition in grey cast iron. It alters the few mechanical properties such as tensile strength, hardness and toughness of grey cast iron and are covered in this review article. It is reported that on increasing the percentage of copper and molybdenum in grey cast iron, tensile strength and hardness increases and impact energy decreases. But, beyond a certain amount of copper and molybdenum addition, there is a negligible effect on the hardness. Thus the main role of copper and molybdenum addition, is to reduce the volume of graphite flakes and increase the content of pearlite in microstructure of gray cast iron.

Effects of heat treatment on microstructure, mechanical and corrosion properties of 15-5 PH stainless steel parts built by selective laser melting process

With recent advancements in additive manufacturing, Selective Laser Melting (SLM) is emerging as an unconventional manufacturing process of exceptional flexibility capable to fabricating any complex part without requiring expensive fixtures, tooling, mold or any other additional auxiliary with a very short lead time from design conceptualization to fabrication. Very few reports are available on the effect of heat treatment on mechanical and corrosion properties of SLM 15-5 Precipitation Hardening (PH) stainless steel. Herein, micro-structural evolution and its correlation with various mechanical and corrosion properties of heat treated SLM 15-5 PH stainless steel are investigated to widen the application of SLM parts for industrial usages. Results show, standard aging condition (H900) increases yield strength, hardness and corrosion resistance through the formation of fine spherical ε-Cu-rich precipitates (∼15 nm), but makes the specimens brittle resulting in an increase in wear rate and a decrease in impact energy. Combined effects of coarsening of elliptical ε-Cu-rich precipitates and increase in reverted austenite phase in overaging (H1150) make the specimen ductile having relatively low yield strength, hardness, wear rate but high impact energy. Solution annealing was found to reduce anisotropy in mechanical properties through the homogenization of microstructure. Higher aging temperature and longer soaking time doesn’t have significant impact on different mechanical properties but deteriorates the corrosion properties. Solution annealing before aging is recommended for the homogeneity in microstructure. Present findings can be used as a guideline to select proper post heat treatment for SLM 15-5 PH stainless steel to impart application oriented mechanical and corrosion properties.

Influence of Tempering Temperature on the Microstructure and Mechanical Properties of a Cr–Ni–Mo‐Alloyed Steel for Rock Drill Applications

This research investigates the mechanical properties of a Cr–Ni–Mo‐alloyed rock drill steel tempered at different temperatures from 150 to 550 °C. The highest strength, hardness, and impact energy occur when the steel is tempered at 180 °C. Strength, hardness, and impact energy decrease with increasing tempering temperature from 180 to 400 °C. For tempering temperatures higher than 400 °C, the steel exhibits: 1) an increase in impact energy; 2) an increase in strength and hardness when tempered at 420, 450, and 480 °C; and 3) a gradual decrease in strength and hardness when tempered at temperature higher than 480 °C. The mechanism of the changes of impact energy and hardness with tempering temperature is proposed.

A Study of Effect of Vanadium on Microstructure and Mechanical Properties of As-Cast and Austempered Ductile Iron

The presence of vanadium, as an alloying element, has various effects on the properties of cast irons. In this research, the effects of adding different amounts of vanadium, including 0, 0.87, and 1.45 wt % V, on the microstructure, the formation of different phases, and the mechanical properties of the as-cast and austempered ductile iron have been investigated. After the casting of samples, preparation of the samples, and determining of their chemical composition, it is austenitization heat treatment at 900°C for 45 minutes and austempering heat treatment at 350°C for 60 minutes that were carried out on the samples. Tensile and impact tests, as well as X-ray diffraction (XRD) analysis and metallography, were conducted to study the mechanical properties and the structure. The microstructures of the samples included carbides in the ausferrite matrix. The results show that with increasing the vanadium, tensile strength and impact energy decrease in as-cast ductile iron, whereas heat treatment can improve them.

Effect of locally increased melted layer thickness on the mechanical properties of laser sintered tool steel parts

Additive technologies have several advantages over conventional manufacturing, such as the freedom of geometry of the products and internal structures. There are also some limitations and problems, deriving from stopping the process during the production. By restarting the process, the building often continues with a thicker starting layer due to the deposition of two or more layers. The effect of skipped melting of layers is investigated in this paper. Maraging steel powder (MS1) was used in direct metal laser sintering (DMLS) process to produce samples with increased thickness of melted layers. The layer thickness was increased in 20 μm steps up to 160 μm with 0.5 mm offset between the increased thickness layers. Porosity caused by the uneven melting was measured by optical microscope, mechanical tests were carried out to quantify the effect of skipped layers and fractured surfaces were observed under SEM. We have found that the yield strength and tensile strength are not affected if the layer thickness is slightly increased locally in the laser sintered part, while even a small increase in porosity greatly reduces the total elongation of the specimen. The decrease of impact energy due to the porosities shows similar correlation with the decrease of percentage elongation at break. However, the Charpy impact test is much more sensitive to layer skipping, the lack of melted layers lowers the impact strength significantly.

Influence of Localized Melting on Dynamic Fracture Behaviours of Metallic Shell

AbstractThe dynamic fracture behaviour of cylindrical shell preformed by localized melting technology was studied experimentally, and the microstructure and performance of melted layers were also analyzed in this paper. The results reveal that the microstructure of melted layer is predominantly needle type and refined martensite by the melted‐solidification process. With the increase of hardness and decrease of impact energy absorbed, the embrittlement tendency of localized melting sample is obviously. Compared with natural fragmentation, the fragments of shell after melting are more regular, and the proportion of effective fragments is high. Due to the sensitivity of shear bands of melted layers, fracture can easily take place along the melting trajectory subjected to internal explosive loading.

Changes in Microstructural and Mechanical Properties of AISI Type 316LN Stainless Steel and Modified 9Cr-1Mo Steel on Long-Term Exposure to Flowing Sodium in a Bi-Metallic Sodium Loop

AISI Type 316LN stainless steel (SS) and modified 9Cr-1Mo steel were exposed to flowing sodium at 798 K (525 °C) for 30000 hours in a bi-metallic sodium loop. The changes in microchemical, microstructural, and mechanical properties were evaluated and compared with the as-received and thermally aged specimens. Effective carbon diffusion coefficient $$ {\left( {D_{\text{C}}^{\text{eff}} } \right)} $$ was calculated to be 6.8 × 10−19 m2/s. Depth of carburization analyzed by secondary ion mass spectroscopy technique was around 100 µm for sodium-exposed 316LN SS. Selective leaching of nickel occurred across depth from the surface of sodium-exposed 316LN SS with the formation of 10 µm ferrite layer, and it showed an increase in yield strength by 15 pct, reduction in ductility by 60 pct, and a decrease in impact energy by 15 pct vis-a-vis the as-received and thermally aged specimens. This reduction in ductility occurred due to extensive precipitation of sigma phase as a result of long-term thermal aging. No significant changes were observed in the sodium/modified 9Cr-1Mo steel interfacial microstructure as well as tensile properties of sodium-exposed modified 9Cr-1Mo steel. Although modified 9Cr-1Mo neither showed carburization nor decarburization on sodium exposure, it showed a drastic reduction in the impact strength, which was attributed to the presence of Laves phase, observed in X-ray diffraction patterns.

Effect of tungsten content on microstructure and mechanical properties of swaged tungsten heavy alloys

This paper describes the effect of tungsten content on microstructure and mechanical properties of swaged Co-containing tungsten heavy alloys with varying tungsten (90W–7Ni–2Fe–1Co, 93W–4.9Ni–1.4Fe–0.7Co and 95W–3.5Ni–1Fe–0.5Co). With increasing tungsten while tensile strength goes through a maximum, both percent elongation and impact energy decrease. Microstructure and fractographic analyses have been carried out in order to explain the trends in mechanical properties. Predominant transgranular fracture of tungsten grains combined with ductile dimple failure of the matrix in 90% W alloy is responsible for superior properties of this alloy in comparison to the alloy with 95% W. The highest tensile strength attained in 93% W alloy is attributed to predominant cleavage failure of W-grains. The results clearly indicate that the matrix volume fraction, contiguity and matrix mean path greatly influence the mechanical properties of tungsten heavy alloys.