A subway car side wall design method and subway car side wall

Abstract

The application discloses a subway car side wall design method and a subway car side wall, and the subway car side wall is composed of side wall modules. The side wall module is composed of a side wall body, a reinforcing rib, a cross beam and a mounting seat, and the side wall body adopts a sandwich structure composed of a panel and a core material. Simulation design is performed by using simulation design software, stress states of each part of the side wall body are obtained through finite element analysis, core material qualities adopted by different parts of the side wall body are determined, and positions and sizes of the mounting beam and the reinforcing rib on the side wall body are determined. The structure and function of the subway car side wall are integrated, the light weight of the subway car side wall is realized under the premise of ensuring the strength and rigidity of the subway car side wall, and the production cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of rail transit technology, specifically to a design method for the side wall of a subway car and the side wall of the subway car. Background Technology

[0002] With the rapid development of subways, lightweighting of subway car sidewalls has become increasingly important. Lightweighting of subway car sidewalls is of particular practical significance for reducing vehicle weight, increasing speed, reducing noise, lowering energy consumption, and improving passenger comfort. Against this backdrop, while ensuring the overall strength of the subway vehicle, interior components have become a key area for lightweighting. Subway car sidewalls account for the largest area of ​​the interior components, and lightweighting them has the most significant effect on overall vehicle weight reduction. Subway car sidewalls are generally divided into non-window area sidewalls and window area sidewalls. Non-window area sidewalls are generally single-curved or planar structures designed according to the curvature of the car body. Window area sidewalls, because they need to fit the window glass, must not only conform to the curvature of the car body but also meet the requirements of the windows on the sidewalls, making their structure more complex.

[0003] Currently, subway car sidewalls primarily use fiberglass and aluminum panels. Fiberglass sidewalls are characterized by relatively simple molding processes and strong shaping capabilities, but they also have relatively poor dimensional stability, low rigidity, are prone to deformation, and are quite heavy. Furthermore, they require metal components to be bonded to the back for mechanical installation. Aluminum panels are not suitable for large-area monolithic molding due to their poor rigidity and susceptibility to deformation. However, subway car sidewalls made from these materials suffer from drawbacks such as high weight for the same structural strength, complex installation, poor overall integrity, and insufficient safety.

[0004] Therefore, the design of subway car side walls requires improvements to the structure, materials, and processing technology. While meeting the strength and rigidity requirements of the car side walls, better structures, more suitable materials, and superior processing technologies should be adopted to achieve lightweighting and reduce production costs.

[0005] According to the patent search, the following patents are mainly related to this application:

[0006] 1. A Chinese invention patent with the application number "201911213280.3", the application date "December 2, 2019", the publication number "CN112977503A", the publication date "June 18, 2021", the title "A side wall panel for a high-speed train carriage", and the applicant "Beijing Xianhe Transportation Equipment Technology Co., Ltd.". This invention patent provides a side wall panel for a high-speed train carriage. The side wall panel of the high-speed train carriage includes a curtain cover plate; a main body, the main body includes a first panel, a second panel, a frame, a first fixing strip, a connecting piece, and a second fixing strip, and the frame is installed at the side wall edges of the first panel and the second panel; the first fixing strip is respectively installed on the side walls of the first panel and the second panel, and the connecting piece and the second fixing strip are respectively installed at the bottoms of the first panel and the second panel, and the frame, the first fixing strip, the connecting piece, and the second fixing strip on the side wall of the first panel are fixedly connected to the frame, the first fixing strip, the connecting piece, and the second fixing strip on the side wall of the second panel correspondingly; a fixing mechanism; an installation groove; an air inlet mechanism; a shock absorption mechanism; a limiting mechanism. However, this patent does not disclose the specific structure of the first panel 21 as the interior panel of the carriage, and does not involve the technical problem of the lightweight of the side wall of the subway carriage.

[0007] 2. A utility model patent with the application number "202021904875.1", the application date "September 4, 2020", the publication number "CN212447529U", the publication date "February 2, 2021", the title "A novel lightweight aluminum alloy subway end wall structure", and the applicant "CRRC Changchun Railway Vehicles Co., Ltd.". This utility model patent includes an upper wall panel and two lower wall panels, and the interfaces between the upper wall panel and the two lower wall panels are fixedly connected by welding. Its characteristics are: the upper wall panel is a large-section lightweight aluminum alloy profile, and the installation parts of the upper wall panel with the top sealing frame of the through passage, the interior top plate of the through passage, and the interior top plate of the end wall are all square cavity structures with one thick wall and three thin walls on one side. The protruding "day"-shaped section of the upper and lower wall panels is the end wall end door frame structure, and the installation part of the lower wall panel with the two side sealing frames of the through passage is a square cavity structure with one thick wall and three thin walls on one side. This utility model provides unified standards for the core structure parameters such as the corresponding aluminum material selection and shape dimensions of the new vehicle type, so as to improve the efficiency of vehicle body design, reduce design risks, and further provide a reference basis for realizing the platformization, standardization, and modularization of the aluminum alloy vehicle body end wall structure. However, this patent uses aluminum alloy profiles as the interior panel of the carriage, which is difficult to carry out special-shaped processing, and has problems of poor heat insulation performance and high cost.

[0008] 3. A utility model patent with application number "201620975257.3", application date "2016.08.30", publication number "CN206171465U", publication date "2017.05.17", titled "A Side Wall Panel for Subway Passenger Interior", and applicant "Qingdao Luomei Weiao New Material Manufacturing Co., Ltd.", which includes a fiberglass wall panel, an aluminum profile window sill, a sealing rubber strip, a window sill fixing profile, and a plug-in connector. The original design included profiles, fiberglass wall panel fixing profiles, baseboards, and latches. The aluminum profile window sills were now fixed using a plug-in connection, with screws used in an inconspicuous location. This simplified installation and ensured a sturdy aluminum profile window sill. The baseboards were glued together, resulting in smaller, more uniform, and aesthetically pleasing seams that were waterproof, moisture-proof, and less prone to detachment. The fiberglass wall panels were streamlined, with the lower part using a plug-in profile connection, the middle section using only one latch, and the top using self-tapping screws. This resulted in a more robust structure and significantly reduced weight after installation. However, the patent did not disclose the specific structure of the interior panel for the subway car, nor did it address the technical issues related to lightweighting the subway car side walls.

[0009] 4. A utility model patent with application number "201420310179.6", application date "2014.06.12", publication number "CN203974820U", publication date "2014.12.03", titled "Assembled Side Wall Panel Structure for Urban Rail Vehicles", and applicant "Changchun Railway Vehicles Co., Ltd.", mainly consists of an assembled side wall panel made of aluminum profiles and aluminum honeycomb. The side wall panel is divided into three parts: upper, middle, and lower. The upper and lower parts are made of aluminum profiles, and the middle part is an aluminum honeycomb structure. The three parts are connected by bolts, and the ends are sealed with aluminum profiles. Mounting seats are provided on the upper and lower aluminum profiles respectively. After assembly, the gaps between the components are uniform, resulting in good aesthetics. It has good overall rigidity and does not deform. It also ensures a uniform space distance between the wall panel and the vehicle body, avoiding environmental pollution and harm to human health. It provides sufficient space for vehicle drainage and wiring of electrical components. When installing the wall panels, the upper and lower mounting brackets of the wall panels are directly connected to the car body's sliding grooves, and workers only need to tighten the mounting bolts. Compared with the previous assembly process of fiberglass wall panels, this reduces the installation steps for workers, improves production efficiency, and reduces the labor intensity of workers. However, this patent does not disclose the specific structure of the interior panel for the car body, nor does it address the technical issues of lightweighting the side walls of subway cars.

[0010] 5. A utility model patent with application number "201721923599.1", application date "2017.12.30", publication number "CN20791620U", publication date "2018.09.28", titled "A Lightweight Vehicle Interior Wall Panel", and applicant "Qingdao Hailiwei New Material Technology Co., Ltd.", includes a lower skin, a core material layer, and an upper skin. The core material layer has a honeycomb structure. The lower skin is fixedly attached to the lower surface of the core material layer, and the upper skin is fixedly attached to the core material layer. The upper skin is fixedly attached to the upper surface of the core material layer; the upper surface of the upper skin is also provided with reinforcing blocks, the reinforcing blocks including a reinforcing layer and an adhesive layer, the reinforcing layer having a mesh structure, the reinforcing layer being semi-embedded and bonded to the upper surface of the adhesive layer, the lower surface of the adhesive layer having several downward protrusions, the lower end of the protrusions being a conical tip, the shape of the protrusions being the same as the inner contour of the honeycomb mesh of the core material layer, the protrusions passing through the upper skin and inserting into the honeycomb mesh of the core material layer, and the lower surface of the adhesive layer being bonded and fixed to the upper surface of the upper skin. However, this patent is a general-purpose interior wall panel, which cannot be applied to parts of subway cars with windows and structural components, and is even less applicable to various irregularly shaped surfaces. Summary of the Invention

[0011] The technical problem to be solved by the present invention is to provide a design method for the side wall of a subway car and the side wall of the subway car, which addresses the deficiencies in the existing technology.

[0012] To solve the above-mentioned technical problems, the technical solution adopted by this invention is: a design method for subway car sidewalls. Based on the location of doors and windows in the subway car sidewall, the sidewall is divided into multiple sidewall modules and numbered. Each sidewall module consists of a sidewall body, reinforcing ribs, and mounting beams. A calculation model is established based on the boundary conditions and stress state of each sidewall module, and calculations are performed using ABAQUS software. The sidewall body adopts a sandwich structure composed of a panel and a core material, with the panel using prepreg. Finite element analysis is used to obtain the stress state of each part of the sidewall module, thereby determining the core material used in different parts of the sidewall body and determining the position and size of the reinforcing ribs and mounting beams within the sidewall body. This achieves structural and functional integration of the subway car sidewall, realizing lightweight design while ensuring the strength and stiffness of the sidewall. Simulation design software is used for simulation design, enabling the design of a subway car sidewall with optimal structure, reasonable stress distribution, simple manufacturing, and low production cost.

[0013] Furthermore, based on the finite element analysis results, it was determined that a high-stiffness core material would be laid in the flat areas of the sidewall body, an easily bendable core material would be laid in the complex curved areas, and a pure composite prepreg would be laid as the core material in the edge areas and areas requiring cutting. The core material and prepreg would be formed by heating and vacuum molding. Different core materials are used according to the stress characteristics of different areas of the sidewall body, fully utilizing the properties of various core materials to meet the strength and stiffness requirements of the sidewall body while facilitating processing and manufacturing.

[0014] Furthermore, based on the finite element analysis results, the location and dimensions of the reinforcing ribs on the back of the sidewall body were determined, and they were integrally formed with the sidewall body through heating and vacuum molding. This ensures a tight bond between the reinforcing ribs and the sidewall body, achieving structural and functional integration.

[0015] Furthermore, based on the finite element analysis results, crossbeams are installed at the upper and lower edges of the back side of the side wall body. These crossbeams are connected to the side wall body using a combination of adhesive bonding and riveting. The crossbeams enhance the strength and rigidity of the side wall body.

[0016] Furthermore, based on the finite element analysis results, the number and spacing of mounting seats on the crossbeams and reinforcing ribs were determined. The mounting seats were connected to the crossbeams or reinforcing ribs using a combination of adhesive bonding and riveting. This ensured the mounting seats were securely connected to the crossbeams and reinforcing ribs, improving the reliability of the connection.

[0017] A subway car sidewall designed according to the above-mentioned subway car sidewall design method is provided. The subway car sidewall is composed of sidewall modules, each consisting of a sidewall body, reinforcing ribs, crossbeams, and mounting seats. Multiple reinforcing ribs are spaced apart on the back of the sidewall body, and crossbeams are located on the upper and lower edges of the back of the sidewall body. Multiple mounting seats are spaced apart on the side of the reinforcing ribs or crossbeams away from the sidewall body. This sidewall body has the advantages of reasonable structure, simple manufacturing, and low production cost.

[0018] Furthermore, the sidewall body is composed of prepreg, core material, and adhesive film. Prepreg is placed on both sides of the core material, and adhesive film is placed between the core material and the prepreg. These are bonded together by heating and vacuum molding to form a sandwich structure. Large, flat areas of the sidewall body use lightweight foam cores as the core material, such as PET foam, aramid honeycomb cores, and fiber-reinforced phenolic foam cores. Complex curved areas of the sidewall body use strong core felt as the core material, while edges or areas requiring cutting use prepreg as the core material. Different core materials are used according to the stress characteristics of different areas of the sidewall body, fully utilizing the properties of various core materials to meet the strength and stiffness requirements of the sidewall body while facilitating processing and manufacturing.

[0019] Furthermore, the reinforcing rib is composed of prepreg, lightweight foam core, and adhesive film. The adhesive film, lightweight foam core, and prepreg are sequentially placed on the back of the side wall body and integrally formed with the side wall body through heating and vacuum molding. This ensures a tight bond between the reinforcing rib and the side wall body, achieving structural and functional integration.

[0020] Furthermore, the crossbeam is made of aluminum profile and is adhesively attached to the upper and lower edges of the back of the side wall body. Countersunk screw holes are provided on the front of the side wall body where the crossbeam is attached. Countersunk screws are inserted into these holes on the front of the side wall body and then threaded onto the crossbeam. The aluminum profile crossbeam has the advantages of being lightweight, high-strength, and rigid, as well as having a long service life and good reliability.

[0021] Furthermore, the mounting base is made of metal and is connected to the reinforcing ribs or crossbeams via adhesive bonding and riveting. Metal mounting bases offer good strength and rigidity, long service life, and high reliability.

[0022] The beneficial effects of this invention are as follows: by using simulation design software for simulation design, the stress state of each part of the side wall body is obtained through finite element analysis, thereby determining the core material used in different parts of the side wall body, and determining the position and size of the installation beam and reinforcing rib on the side wall body; so as to realize the structural and functional integration of the subway car side wall, and achieve the lightweighting of the subway car side wall while ensuring the strength and rigidity of the subway car side wall, thereby reducing production costs. Attached Figure Description

[0023] Figure 1 This is a three-dimensional structural diagram of the front side wall of a subway car.

[0024] Figure 2 This is a schematic diagram of the three-dimensional structure of the reverse side wall of a subway car.

[0025] Figure 3 This is a schematic cross-sectional view of the side wall.

[0026] Figure 4 This is a partial sectional view of the section where the side wall has reinforcing ribs.

[0027] Figure 5 This is a partial sectional view of the section where a beam is located on the side wall.

[0028] In the diagram: 1—prepreg, 2—film, 3—lightweight foam core, 4—reinforced core felt, 5—adhesive, 6—screw, 7—countersunk screw. Detailed Implementation

[0029] The present invention will be further described below with reference to specific embodiments and accompanying drawings:

[0030] A method for designing the side walls of a subway car includes the following steps:

[0031] S1: Based on the location of doors and windows on the side walls of the subway car, divide the side walls of the subway car into multiple side wall modules and number them;

[0032] S2: Based on the boundary conditions and stress conditions of each side wall module, establish a calculation model, use ABAQUS software for calculation, obtain the stress state of each part through finite element analysis, determine the core material used in different parts of the side wall module, and determine the position and size of the installation beam and reinforcing rib on the side wall module.

[0033] S3: By selecting different materials, different reinforcing ribs and installation beam design schemes, finite element analysis is performed to select the optimal design scheme with the best structure, reasonable stress, simple manufacturing and low production cost.

[0034] S4: Prototype the side wall modules based on the preferred design scheme, and identify areas that need further improvement;

[0035] S5: Further optimize the design scheme and determine the final design scheme for the side wall modules;

[0036] S6: Complete the design drawings for the side wall modules based on the final design scheme, and compile the process documents.

[0037] like Figure 1 and 2 As shown, the side wall of the subway car is composed of multiple side wall modules. The side wall modules at different locations in the subway car may be equipped with accessories such as doors, windows, vents, and hooks. However, each side wall module consists of a side wall body 100, reinforcing ribs 200, crossbeams 300, and mounting bases 400. Multiple reinforcing ribs 200 are spaced apart on the back of the side wall body 100, and crossbeams 300 are located on the upper and lower edges of the back of the side wall body 100. Multiple mounting bases 400 are spaced apart on the side of the reinforcing ribs 200 or crossbeams 300 away from the side wall body 100.

[0038] like Figure 3 As shown, the sidewall body 100 is composed of prepreg 1, core material, and adhesive film 2. Prepreg 1 is disposed on both sides of the core material. The prepreg 1 is a continuous fiber or fabric impregnated with a resin matrix. Adhesive film 2 is disposed between the core material and the prepreg 1. The adhesive film 2 is a thermosetting polymer film material. The prepreg 1 and the core material are bonded together by heating and vacuum molding to form a sandwich structure.

[0039] Based on the finite element analysis results, lightweight foam core 3, such as PET foam, aramid honeycomb core and fiber-reinforced phenolic foam core, is used as the core material in the large flat area on the side wall body 100 to increase the strength and stiffness of the large flat area.

[0040] Based on the finite element analysis results, a reinforcing core felt 4 is used as the core material in the complex curved areas of the sidewall body 100. The reinforcing core felt 4 is a felt-like material composed of polyester fibers or glass fibers and microspheres, bonded together with an adhesive. The reinforcing core felt 4 is easy to bend to fill complex curved areas.

[0041] According to the finite element analysis results, the edges of the side wall body 100, window frames, door frames, installation beams 300, or areas that need to be cut are subjected to greater stress and stress concentration. Therefore, high-density prepreg 1 is used as the core material to enhance the strength and stiffness of these areas.

[0042] During manufacturing: Prepreg 1 is laid inside the sidewall body mold, then film 2 is laid on the prepreg 1. Depending on the area, lightweight foam core 3, reinforcing felt 4, or the core material of prepreg 1 is placed on film 2. Film 2 is then laid on the core material, and finally, prepreg 1 is laid on film 2. The entire sidewall body mold is placed in a vacuum bag, the mold is heated, and the air in the vacuum bag is removed, pressing the vacuum bag tightly against the sidewall material. The sidewall material is integrally molded through heating and vacuum molding to form the sidewall body.

[0043] like Figure 4 As shown, the reinforcing rib 200 is composed of prepreg 1, lightweight foam core 3, and adhesive film 2. Adhesive film 2, lightweight foam core 3, and prepreg 1 are sequentially arranged on the back of the sidewall body 100. The lightweight foam core 3 is machined. Adhesive film 2, lightweight foam core 3, and prepreg 1 are placed sequentially at predetermined positions on the back of the sidewall body 100 and integrally formed with the sidewall body 100 through heating and vacuum molding. This ensures a tight bond between the reinforcing rib 200 and the sidewall body 100, achieving structural and functional integration.

[0044] like Figure 5 As shown, the crossbeam 300 is made of aluminum profile and is attached to the upper and lower edges of the back of the side wall body 100 using adhesive 5. A countersunk screw hole is provided on the front of the side wall body 100 where the crossbeam 300 is attached. The countersunk screw 7 passes through the screw hole on the front of the side wall body 100 and is threaded to the crossbeam 300. The mounting base 400 is made of metal and is connected to the reinforcing rib 200 or the crossbeam 300 by adhesive and riveting.

[0045] In summary, the beneficial effects of this invention are as follows: by using simulation design software for simulation design, the stress state of each part of the side wall body is obtained through finite element analysis, thereby determining the core material used in different parts of the side wall body, and determining the position and size of the installation beam and reinforcing rib on the side wall body; so as to realize the structural and functional integration of the subway car side wall, and achieve the lightweighting of the subway car side wall while ensuring the strength and rigidity of the subway car side wall, thereby reducing production costs.

[0046] The above embodiments are for illustrative purposes only and are not intended to limit the invention. Those skilled in the art can make various changes or modifications without departing from the spirit and scope of the invention. Therefore, all equivalent technical solutions should also fall within the protection scope of the invention, which should be defined by the claims.

Claims

1. A method of designing a subway car side wall, the method comprising: Each side wall module is composed of a side wall body (100), a reinforcing rib (200) and a mounting beam, the side wall body (100) adopts a sandwich structure composed of a panel and a core material, and the panel adopts a prepreg (1); the stress state of each part of the side wall module is obtained through finite element analysis to determine the core material quality adopted by different parts of the side wall body (100) and the position and size of the reinforcing rib (200) and the mounting beam on the side wall body (100); the core material with high rigidity performance is laid on the flat area of the side wall body (100), the core material easy to bend and form is laid on the complex curved surface area, and the pure composite prepreg (1) is laid as the core material on the edge part and the area needing cutting, and the core material and the prepreg (1) are formed through heating and vacuum molding; the structure and function integration of the side wall of the subway car is realized, and the light weight of the side wall of the subway car is realized under the premise of ensuring the strength and rigidity of the side wall of the subway car; ​ The method comprises the following steps: S1: according to the door and window positions of the side wall of the subway car, the side wall of the subway car is divided into multiple side wall modules and numbered; S2: according to the boundary conditions and stress state of each side wall module, a calculation model is established, ABAQUS software is used for calculation, the core material quality adopted by different parts of the side wall module is determined, and the position and size of the mounting beam and the reinforcing rib on the side wall module are determined; S3: different material quality, different reinforcing rib and mounting beam design schemes are selected for finite element analysis, and the optimal design scheme is selected from them; S4: the side wall module is trial-produced according to the optimal design scheme, and the further improvement is found out; S5: the design scheme is further optimized, and the final design scheme of the side wall module is determined; S6: the design drawings of the side wall module are completed according to the final design scheme, and the process file is prepared; During manufacturing: the prepreg (1) is laid in the side wall body mold, then the adhesive film (2) is pasted on the prepreg (1), then the core material of the light foam core (3), the strong core felt (4) or the prepreg (1) is placed on the adhesive film (2) according to different areas, then the adhesive film (2) is pasted on the core material, and finally the prepreg (1) is pasted on the adhesive film (2), the side wall body mold is put into the vacuum bag as a whole, the side wall body mold is heated, and the air in the vacuum bag is extracted, so that the vacuum bag is tightly pressed on the side wall raw material, the side wall raw material is integrally formed through heating and vacuum molding, and the side wall body is formed.

2. The method of designing a subway car side wall according to claim 1, wherein: According to the finite element analysis result, the position and size of the reinforcing rib (200) arranged on the back of the side wall body (100) are determined, and the side wall body (100) is integrally formed through heating and vacuum molding.

3. The method of designing a subway car side wall according to claim 2, wherein: According to the finite element analysis result, the cross beam (300) is arranged on the upper and lower edges of the back of the side wall body (100), and the cross beam (300) is connected with the side wall body (100) through gluing + riveting.

4. The method of designing a subway car side wall according to claim 3, wherein: According to the finite element analysis result, the number and spacing of the mounting seat (400) arranged on the cross beam (300) and the reinforcing rib (200) are determined, and the mounting seat (400) is connected with the cross beam (300) or the reinforcing rib (200) through gluing + riveting.

5. The subway car side wall designed by the method according to any one of claims 1 to 4, characterized in that: The side wall of the subway car is composed of side wall modules, the side wall module is composed of a side wall body (100), a reinforcing rib (200), a cross beam (300) and a mounting seat (400), a plurality of reinforcing ribs (200) are arranged on the back of the side wall body (100) at intervals, the cross beam (300) is arranged on the upper and lower edges of the back of the side wall body (100), and a plurality of mounting seats (400) are arranged on the side away from the side wall body (100) of the reinforcing rib (200) or the cross beam (300) at intervals.

6. The subway car side wall designed by the method of claim 5, wherein: The side wall body (100) is composed of a prepreg (1), a core material and a film (2), the prepreg (1) is arranged on both sides of the core material, the film (2) is arranged between the core material and the prepreg (1), and a sandwich structure is formed by heating and vacuum molding; a large flat area on the side wall body (100) adopts a light foam core (3) as a core material, a complex curved surface area on the side wall body (100) adopts a strong core felt (4) as a core material, and the edge of the side wall body (100) or the area to be cut adopts the prepreg (1) as a core material.

7. The subway car side wall designed by the method of claim 6, wherein: The reinforcing rib (200) is composed of a prepreg (1), a light foam core (3) and a film (2), the film (2), the light foam core (3) and the prepreg (1) are sequentially arranged on the back of the side wall body (100), and the side wall body (100) is integrally formed by heating and vacuum molding.

8. The subway car side wall designed by the method of claim 7, wherein: The cross beam (300) is an aluminum profile, is adhered to the upper and lower edges of the back of the side wall body (100) by using an adhesive (5), a screw hole with a countersunk head is arranged on the front of the side wall body (100) to which the cross beam (300) is adhered, and a countersunk screw (7) is screwed into the screw hole from the front of the side wall body (100) and is connected with the cross beam (300) by screwing.

9. The subway car side wall designed by the method of claim 8, wherein: The mounting seat (400) is made of metal material and is connected with the reinforcing rib (200) or the cross beam (300) by gluing and riveting.

Images